TL;DR
- Google may rewrite a title tag that is half-empty, near-duplicated across pages or does not match the content, and displayed titles are cut by screen width, not a fixed character count.
- The meta description is not a direct ranking signal; Google may show page text instead, and it ignores the meta keywords tag entirely.
- Keyword stuffing falls under Google's spam policies; place the main keyword in the title, H1, first paragraph, one H2, the URL and main image alt text.
- Search Console queries at roughly position 8-20 with high impressions are the fastest on-page wins: rewrite the title, fill missing answers, add internal links.
On-page SEO is the work of improving everything on the page itself so Google understands which query the page answers and the person who clicks finds what they came for. That covers the title tag, meta description, H1-H3 headings, URL, body content, internal links and image alt text, all of which a site owner can change today without waiting for another site to link in, which is what separates it from off-page work.
This guide explains how on-page SEO differs from off-page and technical SEO, how each on-page factor works, where to place keywords and how often, which tools to audit with, and how long changes take to show. It ends with a checklist you can run against your own pages.
What on-page SEO is and how it differs from off-page and technical SEO
The simplest way to split them is to ask where the thing you are fixing lives. If it lives on the page and a reader sees or uses it, such as headings, text, images or links in an article, it is on-page. If it lives outside your site, such as other sites linking to you, press mentions or reviews on other platforms, it is off-page. Technical SEO is the infrastructure that lets Google crawl and index the site: robots.txt, sitemaps, canonicals, load speed, mobile rendering and HTTPS.
The three depend on each other. A page with excellent content that is blocked by noindex will not rank at all. A page with perfect technical setup whose title says "Home" and whose content does not answer the query will not rank either. Links from other sites add credibility, but if the destination page does not match what people search for, links can only do so much.
Some items overlap. Structured data (schema) is filed under technical by some people and under on-page by others, because it sits in the page's own code. Page speed depends partly on image file sizes, which the content writer uploads. Which bucket a task belongs to matters less than having someone clearly responsible for it.
Which on-page factors you need to work on
These are the main elements to check on every page you want to rank, in roughly the order Google and users encounter them.
Title tag
The title tag is the text in the page's <title> element. Google uses it as the main source for the "title link", the blue headline people see in search results, but Google can rewrite it if the original does not match the content, is half-empty, or is near-duplicated across pages. What gets displayed is cut off by screen width rather than a fixed character count, so put the important words near the start.
The practical rule: one page, one title that no other page shares, stating clearly what the page is, with the main keyword included naturally and the brand name at the end if there is room. Illustrative example: an online shoe shop has a category page titled "Category | ShopName". Changing it to "Women's Running Shoes, Soft Cushioning, Free Delivery in Thailand | ShopName" tells both Google and searchers immediately what the page sells.
Meta description
The meta description is a short summary that Google may show under the title link in results. Google says it may use text from the page instead when that text answers the user's query better. The meta description is not a direct ranking signal, but it affects whether people click, so write it to summarise what the page contains and why someone should click. Each page should have its own description rather than one line reused across the whole site.
As for the meta keywords tag that some content management systems still offer a field for, Google announced long ago that it does not use it for ranking. Leaving it empty costs nothing.
H1, H2 and H3 headings
Headings break content into sections so readers can scan quickly and Google can see the structure of the topic. The H1 is usually the page title, H2s are the main sections, and H3s are subsections under an H2. Google has no rule that a page must have exactly one H1, but a single H1 that matches the page topic keeps the structure easier to read and maintain.
A common mistake is using heading tags just to make text bigger, for example putting a phone number or promotion in an H2, which muddles the outline. Another is a theme that wraps the logo in an H1 on every page, so every page has the same H1. Check the actual page source, not just how it looks on screen.
URL
Google recommends URLs that people can read and understand, using descriptive words separated by hyphens (-) rather than underscores (_). A URL like /product?id=48213 works, but tells the user nothing, while /running-shoes-women/ says what the page is about straight away.
Thai sites have an extra decision. Thai-script URLs work and Google reads them, but when copied into LINE or email they often turn into a long string of % characters (percent-encoding), because Thai characters have to be encoded in URLs. Both approaches can rank. Pick one and use it consistently across the site. More important: never change the URL of a page that already ranks without a 301 redirect to the new URL.
Content that actually answers the query
This is the heaviest part of on-page work. Before writing, search the main keyword in Google and look at what type of pages rank: explanatory articles, product pages, comparison pages or list pages. If nearly all results are how-to articles and your page is a sales page, even a perfect title will struggle, because the page format does not match the searcher's intent (search intent).
Next is completeness. Look at the "People also ask" box and the related searches at the bottom of the results, and ask whether your page answers those questions yet. Content should include information readers can use, such as steps, real product specifications, conditions, prices or limits, rather than broad paragraphs that repeat other sites. Longer content does not always win. Content that answers directly and completely does.
Internal links
Internal links point from one page to another on the same site. Google uses them to discover new pages and uses the link text (anchor text) to understand what the destination page is about. Google recommends descriptive anchor text: "how to choose running shoes for beginners" works better than "click here" or "read more".
A page with no internal links pointing to it (an orphan page) may not be found by Google or may be treated as less important. A simple fix: every time you publish a new article, go back and add links from two or three related older articles, and link from the article to the relevant service or product page.
Image alt text
Alt text is the text in an image tag's alt attribute. Google uses alt text together with image analysis and the surrounding content to understand what an image shows, which also affects how it appears in Google Images. Screen readers for visually impaired users read this text aloud.
Describe what is actually in the image, for example "pink women's running shoe with thick foam sole, side view", not "IMG_0042" and not a string of repeated keywords. Purely decorative images can have an empty alt.
Structured data
Structured data is code that tells Google directly what the information on the page is, such as a product, a price, an article or a list of frequently asked questions. It makes a page eligible for rich results, but does not guarantee they will show. You can validate it with Google's Rich Results Test, and the data in your schema must always match what users see on the page.
Where to put keywords and how many times
There is no correct fixed count. Repeating a keyword until the text reads unnaturally (keyword stuffing) is covered by Google's spam policies and can cost the page its rankings.
Places where the main keyword or a close variant should appear naturally:
- The title tag, near the start if possible
- The H1 or page headline
- The first paragraph, which answers the main question straight away
- At least one H2, in the form people actually type
- The URL, if the page is new
- The alt text of the main image, if the image genuinely relates to the keyword
For the rest of the article, use synonyms, related terms and the sub-questions people search alongside it. Google understands close meanings well. Thai has a particular wrinkle: people search the same topic in several forms, such as "on page seo", "on-page seo", the Thai transliteration, or Thai mixed with English. There is no need to repeat every form. Pick the one people use most as the main term and let the others appear where the content naturally calls for them.
Also watch for several pages targeting the same keyword (keyword cannibalization). If you have three articles titled "what is on page SEO" written at different times, they compete with each other. Merge them into the single most complete page and 301-redirect the others to it.
On-page SEO checklist
Run this checklist one page at a time, starting with the pages that matter most to the business: main service pages, best-selling product categories, or articles with high impressions but low positions.
- The page has one clear main keyword, and no other page on the site targets the same term
- The page format matches the results that rank (article, product page or comparison)
- The title is unique, states the topic clearly and includes the main keyword
- The meta description summarises the content and gives a reason to click, and is unique
- There is an H1 that matches the topic, with H2s and H3s in a logical order
- The first paragraph answers the main question within two sentences
- The content answers the related questions in "People also ask"
- The URL is short and readable, and is never changed without a redirect
- Related pages link to this page, and this page links out to pages that help the reader next
- Every meaningful image has descriptive alt text and the files are compressed
- Structured data (if present) passes the Rich Results Test and matches the visible content
- The page has no accidental noindex, and the canonical points to itself (or to the intended page)
Item 12 is technically a technical task, but it is included because it can stop a page that ticks every on-page box from ranking at all. You can check it with URL Inspection in Search Console.
On-page factors at a glance: what Google uses them for and where they go wrong
| Element | What Google uses it for | Common mistake |
|---|---|---|
| Title tag | Main source of the title link in results; Google may rewrite it | Same title on many pages, or only the brand name |
| Meta description | May be used as the snippet under the title link; not a direct ranking signal | One description copied across the whole site |
| H1-H3 headings | Helps it understand the structure and topics of the content | Headings used to enlarge text, or the logo as H1 on every page |
| Internal links | Discovers new pages and uses anchor text to understand the target | "Click here" anchors, or orphan pages |
| Alt text | Used with image analysis to understand images and show them in Google Images | Left as a file name, or stuffed with keywords |
Which tools to audit on-page SEO with
Free Google tools are enough to start.
- Google Search Console: the Performance report shows the queries a page gets impressions for, clicks, CTR and average position. Filter by page to see which queries it is found for. The URL Inspection tool tells you whether the page is indexed and which canonical Google chose, and its Request Indexing button can be used after you update an important page.
- Lighthouse in Chrome DevTools (right-click, Inspect, then the Lighthouse tab) has an SEO category that checks the basics: whether there is a title, a meta description, alt attributes on images and descriptive link text.
- PageSpeed Insights checks speed and Core Web Vitals (LCP, INP, CLS), using real-user data where available plus lab data.
- Rich Results Test checks that structured data is valid and which rich results the page is eligible for.
Once a site runs to hundreds of pages, checking one page at a time stops being practical. Use a crawler that collects data across the whole site, then review reports for duplicate titles, empty meta descriptions, missing H1s, images without alt text and pages with no internal links pointing to them. Fix in order of page importance.
A quick-win method in Search Console: open the Performance report, choose the last three months, turn on the average position column, and filter for queries sitting at roughly position 8 to 20 with high impressions. Google already considers these pages relevant. Rewriting the title to match the query, adding sections that answer missing questions and adding internal links pointing in is usually easier than starting a new page from scratch.
How long on-page SEO takes to show results
Nobody can give an exact number. Google itself says some changes may take effect within a few hours while others can take several months. First Google has to recrawl the page.
Title and meta description changes tend to show sooner, because they change what people see in results and show up as CTR changes in Search Console once Google has recrawled the page. Rewriting content or restructuring a page usually takes longer and depends on how competitive the keyword is.
A straightforward way to measure: record the date of each change (in a Search Console annotation or a spreadsheet), then compare equal periods before and after, for example 28 days before against 28 days after Google has recrawled the page. Look at impressions, clicks, CTR and average position for that page, filtered to the queries you targeted. Illustrative example: a page with 4,000 impressions and 40 clicks in 28 days (1% CTR) gets 4,200 impressions and 84 clicks (2% CTR) after a title rewrite. That means the title change worked on clicks even though position did not move. These numbers only show how to read the result. They are not an expected outcome.
Two cautions. Do not change several things on one page at once and then conclude which one worked. And do not judge from a few days of data, because rankings already swing with the day of the week and the season.
On-page SEO for websites in the Thai market
The same topic may be searched as "on page seo คือ", a Thai transliteration, or a Thai phrase describing SEO on the web page. Check in Search Console which form your page actually gets impressions from, and use that form in the title and H1.
Sites in both Thai and English should give each language its own title, meta description and alt text, rather than leaving Thai pages with an English title inherited from the theme, and should set hreflang so Google knows which pages are translations of each other. Finally, make sure important content appears in full on mobile and is not hidden or cut from the mobile version, because Google mainly uses the mobile version for indexing.
On-page SEO FAQ
Should on-page or technical SEO come first?
Check a few technical basics first: the page is not set to noindex, robots.txt does not block it, and Search Console shows it as indexed. Then put the effort into on-page, because if Google cannot reach the page, on-page work has no effect at all.
Does the meta description affect rankings?
Not directly. Google uses the meta description as a candidate for the snippet under the title link and may choose text from the page instead. Its real value is helping people decide to click, which you can measure as CTR in Search Console.
How many words does an article need to rank?
Google sets no minimum length. The right length is whatever it takes to answer the query fully. Look at which topics the ranking pages cover, then make your page answer them more completely and clearly, not at greater length.
Why is a page still not ranking after full on-page work?
Likely causes include a page format that does not match search intent, or a keyword where competitors have far more authority, which needs off-page work as well. Several pages on your site competing for the same keyword is another. Check all three before rewriting the title yet again.
Start with the pages that matter most
On-page SEO is not a one-off job. Pages gain new content, queries change, and competitors keep improving their pages. If you want specialists to audit the whole site and prioritise which pages to fix first, see our SEO audit service. For a full SEO plan covering on-page, technical and off-page, see SEO services in Thailand. For sites that need new content built around real search queries, see content marketing, and if the existing site structure is holding you back, see web design.
