@Ant **********
Ok, I understand, there’s a financial requirement for to apply for a 90 days Non O visa and do yearly extension of stay in Thailand.
If you don’t have any income or pension you’ll need to prove funds equal to 800K baht at home to apply and 800K baht in a Thai bank for the future.
If you want to do a longer stay with less financial requirements you could apply for a six months multiple entries tourist visa. This gives you up to nine months in Thailand in the first place.