Get a visa due to retirement (OA) in your home country, then if you want to stay longer than one year, that can be extended within Thailand as long as you meet the financial requirements. 800,000b in a thai bank, 65,000 monthly income or a combination of the 2.
North Thailand is cooler and seems more of a 'hub' for alternative therapies/etc so might suit you.
Get a visa at a Thai embassy/consulate and then after the initial year, it can be extended within Thailand. You will need 800,000b in a Thai (sole) bank account/income of 65,000pm or a combination of the 2. With that you can extend your visa because of retirement in the Kingdom