What steps do I need to take to translate and legalize my marriage certificate in the UK for my Non-O visa extension in Thailand?

The 'marriage' paperwork is not insane. It might take up a couple of hours of your time once a year. If you scan and save passport pages, house book, wife's id, marriage certs etc etc, then you just print them off again next year. Easy peasy.

If you really want to go the harder marriage way:

Make sure your marriage is accepted in Thailand. Go ask your Thai embassy, you may need to get some paper/stamp!

But I would choose the retirement way with 800k in bank. It’s way easier for you and the immigration.

use your own 800k and get the retirement if your old enough far less hassle

You don't need a law firm

Do it all in bangkok only thing you will need from your embassy in bangkok is a translated stamped copy of your passport bring any previous marriage papers I.e. divorce certificates and do the rest in bangkok

Contact an immigration law firm in Bangkok,

Get your UK marraige certificate translated and certified by the Thai Embassy it will make things a little easier.

I would go for the retirement visa instead. Less hassle.

Document Legalisation at RTE London

Once you have the original back from FCDO with its attached certified Apostille, they need :

1. The original document(s) to be legalised, certified by FCDO (UK)

2. A copy of every single page including an apostille page from FCDO (UK)

3. Legalisation application form and a copy of applicant's passport for reference (* * Non-Thai can omit this requirement)

4. A fee of £10per documentis required (can be paid by debit card/contactless or cash) ed to be translated. RTE London have a list of "approved" translators in UK on their website

Applications for document legalisation should be submitted to The Consular Section, Royal Thai Embassy, 29 Queen's Gate (Basement) , London SW7 5JB

Get your document legalised (UK government) -

Apply for legalisation -

RTE London document translation and legalisation - -legalisation?menu=5d6636ce15e39c3bd44&fbclid=IwY2xjawHB6EFleHRuA2FlbQIxMAABHcGehPfMstezUMge69FCtzPl4sCgoJM_9Vnh21Hyb51WQo6_gw9LAj7d8g_aem_tXfbDqk-VZE58rfrVotPZg

1. IN THE UK: Marriage certificate legalised by the FCDO in Milton Keynes

2. IN THE UK Marriage Certificate AND the Apostille from the FCDO Translated

3. IN THE UK: Marriage Certificate AND the Apostille from the FCDO AND their translations verified by the Thai Embassy in London

4. IN THAILAND: All the above (ie all 4 documents & their translations, making 8 in total) Legalised by MFA in Bangkok