Here's the website to make an appointment to get a notary letter from the US consulate in Bangkok.
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Here's the standard affidavit you can fill out (but DON'T sign it) so you can prove residency.
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/02/blank-affidavit-bangkok.pdf
The good news is, IF you are already married you can also get a 60 day (visit family) extension on that 90 day Non-O stamp you entered on if you run outta time. After that you can apply for the yearly extension of stay