Good afternoon
Can I verify that the advise I found on this group for marriage certificates is still valid ** as we are both uk nationals with a marriage certificate that we need authorising for our next year extension .
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Thailand is not a signatory to the apostille treaty so the apostille is not recognized as certification/authentication in Thailand.
Go to the embassy and get them to either "authenticate it" or swear an affidavit of authenticity in front of the consular officer.
You then go to the Thai Ministry of Foreign Affairs at Government Complex (Chengwattana) and get their stamp on it.
Now you are authenticated and good for use in Thailand.
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Many thanks
TLDR : Answer Summary
The post discusses the process of authenticating a UK marriage certificate necessary for visa extensions in Thailand. It clarifies that Thailand does not recognize the apostille due to its non-signatory status to the apostille treaty. Therefore, one must go through the UK embassy for authentication or an affidavit, followed by getting it stamped at the Thai Ministry of Foreign Affairs. A comment adds that if the marriage took place in the UK, the certificate needs to be sent back to the UK for legalization at the Thai embassy, as in-country legalization is no longer an option.