What is the process for changing a yearly visa extension based on marriage in Thailand, and what are the requirements for proof of funds?

Just an update about Buengkan immigration office.

Went there today, me and another person to do our 90 day check in. That was both done in a few minutes.

The person I was with, wants to change his yearly extension to being based on marriage, from the based on being over 50 that he has now, when applying next time in October.

We asked about proof of funds if using income method, as our embassy is one of the 4 that no longer providing the affidavit and the person I was with has used income method for many years. He just wanted to know in good time, what specific paperwork was needed in this case.

The answer was very clear.

12 months of bank statements showing international transfers will be accepted along with a bank letter. No further documentation of funds needed. That might also mean that there is no leniency regarding extensions based on being over 50, if having less than 12 months of transfers. But in this case it's irrelevant as there are years of transfers each and every month, well above the requirements for extension based on marriage.

All in all, very polite, efficient and friendly service as always there.