Apply Non-o in home country. On arrival immediately open a Thai bank account and put 800k baht in after 2 months apply for 1 year extension and leave money in for another 3 months. Cannot go lower than 400 k and MUST be back to 800k 2 months before the day you apply for next extension NOT the day your previous extension finishes
You will enter on 30 day exempt. Then leave an buy a Non-o which is valid for 90 days. Then for your 1 year extension which can only be purchased in Thailand you will most definitely need 400k in your Thai bank account