What documentation do I need to apply for a further extension of stay based on marriage to a Thai national after buying property?

Seasoning for 0 Baht is 2 months before your application date.

you can apply for a new extension at MOST offices when you have 30 days or less left on your current stamp.

The process is the same as last year, apply with the correct documentation, pay the 1900baht, get a 30 day under consideration stamp, they come do a home visit and when that 30 days is up you go back and get the stamp in your passport for the year extension.

IF you already have a TM30 filed showing you stay where you stay (which you do whether you rent or own) the only differnce is this year you don't show a rental agreement but the title deed (chanote) with your name on it

You DO apply before the current extension runs out.

You need to understand that once you apply and get the 30 day under consideration stamp you HAVE to go back to the immigration office on that date to get the new extension inked in or you lose the whole thing and start over.

Hopefully you can coordinate your leaving with your applying for the year extension so you're in country during the process.

GO to your immigration office with your thai wife, get the hand out listing the current requirements, photos, bank letters, etc well before you're going to apply for the extension so you can pull it off with just one try 🙂