Not everyone who wants to retire in Thailand is required to pay taxes; only retirees who have income profits inside of Thailand are required to pay taxes. Applicants, who have an income from overseas profits will not be required to pay any taxes in Thailand."
I always say to seek professional advice from a tax accountant as your individual circumstances may be different.
Non o or non oa visa based on retirement but you will need ฿800k in the bank. The alternative is a Non O where they provide ฿800k and open a bank account for you. Recommend Bangkok bank.