Can I Change My Retirement Visa to a Marriage Visa in Phuket with My Translated Marriage Certificate?

My translation was done by a company in BKK which then sent it to MFA for their stamp of approval... It's the MFA stamp I think the Amphur will be looking for...not the actual translation....

Well very easy..take ist to the Bangkok Translation For example to make their "Stamp " it a certificated translation office very close to the intersection up to the rang hill....it's not enough by a foreign office ...but they are easy and you get it

I did a similar thing in Phayao Amphur Oct 2017 for my Thai wife since our NZ wedding 1972.. They wanted a certified transcription which we had to go to BKK for. No problem - though once we had that they changed her legal surname to the same as mine, gave a flowery certificate of the name change which she used for her Thai ID and then a fresh new Thai passport in the new 5 year old surname.

Yes exactly and also the one with the flowers around the borders

I got that green and red round stamp at the Thai Consulate in Los Angeles after I had the marriage license first authenticated from the US state department and then translated into Thai

Took all of that to the local amphur in Prachinburi and registered our marriage in Thailand

Immigration then wanted all of that including our US marriage certificate when we applied for my one year extension based on marriage

IF you need to officially register your marriage in Thailand, this is definitely the correct steps based on my experience and advice saught from the national hotline:

I also assume you are Thai or are married to a Thai.

You need to seek advice from the Thai embassy in your other country (you only said somewhere in the EU or Europe). This is because your marriage cert from that country MAY need to be certified by the govt of that country first. Additionally, the same Thai embassy MAY also need to certify that very same document. Once your paperwork is in Thailand, calling your local registrar office for advice is very important as you will likely need to have it translated into Thai. The Thai translation and the Embassy's certification then need to be legalised by the Dept of Consular Affairs at Chaengwattana.

For example, in the UK:-

You need to get your UK certified by FCO (Foreign & Commonwealth Office). Then send everything you rec back from FCO to the Thai Embassy in London so they certify it. Once in Thailand you then have the document rec'd from the Thai Embassy translated and legalised by the Dept. of Consular Affairs.

Note: Very few registrar offices might not require the Dept of Consular Affairs' legalisation hence contacting them is important but you still need to take the previous steps.

Last but not least, it MIGHT be cheaper/less time-consuming to get a Thai marriage cert done instead. Again check with your local Amphor as to what documents are needed such as certification of your foreign spouses's passport, two witnesses etc.

Best of luck.