When is the best time to apply for a one-year extension of stay based on marriage to a Thai national?

@John *******

I'd swing by the immigration office with your thai wife in tow, well BEFORE you're going to apply for the year extension and get the hand out from them that lists the documentation requirements they want at that particular office. That way you can have your ducks in a row and quacking in time when you go back to get the extension..

Good luck with it (y)

@John *******

you are NOT required to have insurance to get a year extension of stay based on marriage to a thai. That was an ENTRY requirement and has nothing to do with getting an extension inside the country.