Bilingual website SEO: how to rank in English and Thai

What does a bilingual website need for SEO?

A bilingual website needs each language to work as a complete, crawlable site of its own, connected to the other by clear signals. In practice that means five things:

1. A separate URL for every page in every language, so search engines can index both.
2. hreflang annotations linking each page to its equivalent in the other language.
3. Native copy in each language, written or thoroughly edited by fluent writers.
4. Localised metadata: titles, meta descriptions, image alt text and structured data in the page’s own language.
5. A visible language switcher that takes people to the same page in the other language, not back to the homepage.

Get these right and each language can compete on its own searches. Get them wrong and the usual result is that Google indexes one language well and largely ignores the other.

Subfolders, subdomains or separate domains: which URL structure is best?

For most small and mid-sized businesses, subfolders such as example.com/en/ and example.com/th/ are the simplest and strongest choice. Both languages share one domain, so the reputation the site earns benefits both.

The last option is the most common mistake. Google advises against showing different languages on the same URL based on cookies or browser settings, because its crawler usually sees only one version, so the other language never gets indexed.

How does hreflang work?

hreflang is an annotation that tells search engines which language a page is in and where its equivalents in other languages live, so each searcher is shown the right version. It does not translate anything or raise rankings; it prevents the wrong language being shown.

Each page lists every language version, including itself. For an English services page with a Thai equivalent, the annotations would contain:

The Thai page carries exactly the same three annotations. The rules that trip people up:

• Links must be reciprocal. If the English page points to the Thai page, the Thai page must point back, or the pair may be ignored.
• Use valid codes: ISO 639-1 for language (th, en), optionally followed by an ISO 3166-1 country code (th-TH, en-GB). “en-UK” is a common error; the correct code is en-GB.
• Use full, absolute URLs that return a 200 status, are indexable and are the canonical version. Never point hreflang at a redirect.
• Keep canonicals within each language. The Thai page’s canonical should be the Thai page, not the English one.
• Choose one method: link elements in the page head, HTTP headers (useful for PDFs) or entries in your XML sitemap.

Also set the html lang attribute on each page (lang="th" on Thai pages). Google says it detects language from the visible content rather than this attribute, but it helps browsers, screen readers and other tools.

Why shouldn’t you machine-translate your Thai pages?

Machine translation produces text that is understandable but rarely persuasive, and it often misses how Thai customers actually search and speak. Google’s spam policies have long listed text translated by an automated tool without human review as an example of low-value automated content, so publishing raw machine output at scale is a risk as well as a missed opportunity.

• Register and tone. Thai has levels of formality and polite particles that change how a business sounds. A direct translation of breezy English copy can read as odd or careless.
• Different search phrasing. Thai searchers mix Thai script with English brand and treatment names, and use their own common terms. An aesthetic clinic might be searched as “คลินิกความงาม ทองหล่อ” rather than a literal translation of its English keyword.
• Trust. Awkward Thai signals that the business does not really serve Thai customers, which is the opposite of what a bilingual site is for.

Machine translation can be a useful first draft, but every page should be rewritten or carefully edited by a fluent writer before it goes live.

How do you research Thai keywords?

Research Thai keywords from scratch rather than translating your English list. Thai and English speakers frame the same need differently.

1. Ask your Thai-speaking staff and customers how they would describe each service in a search or a LINE message.
2. Use Google autocomplete in Thai and note the “People also ask” questions that appear for Thai queries.
3. Check spelling and transliteration variants. Thai has no spaces between words and English loanwords can be spelt several ways in Thai script.
4. Watch mixed-language searches, where an English brand or treatment name sits inside a Thai query.
5. Filter Search Console by country and by Thai-language queries once the site is live to see what is actually working.

What else needs translating besides the page copy?

Everything a visitor or search engine reads should exist in the page’s language: title tags, meta descriptions, headings, image alt text, button labels, form fields and error messages, confirmation emails, and structured data, which should carry an inLanguage value and translated names and descriptions.

A few practical decisions are worth making early. URL slugs under /th/ can be romanised English words or Thai script; Thai characters work but become long, unreadable codes when copied and shared, so many sites keep short English slugs. Do not redirect visitors automatically by location or browser language; let them choose, and remember the choice. And use a font that renders Thai tone marks clearly with enough line height. For local search, keep one Google Business Profile per location and make sure the address on both language versions of your site matches it, as covered in our local SEO guide.

At PJW Partners, websites can launch in English and Thai from day one, with native copy, correct hreflang and bilingual schema markup. You can see the approach in our bilingual Na Clinic website with online booking, and our clinic website design guide covers more. If you are planning a bilingual site, tell us about your audience and we will suggest the right structure.

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