Given the recent changes in what is commonly called a "retirement visa" (that you get IN country at the immigration office and which is really a yearly extension of stay) where the consulates of 4 countries stopped issuing income affidavits to meet the financial requirements based on monthly income <- meaning you transfer at least 65K baht a month into a bank account from overseas for 12 months before you apply for your extension
AND
the change yesterday of the banked money method where you bank 800K baht in a thai bank account in your name for 2 months prior to your extension, and then show 800K baht still in the account and you can NEVER take out more than 400K baht for the rest of the year.
I would strongly suggest to ANYONE comin' here thinking they're going to rock up and get a 'retirement visa' in country to get a year-long, multi-entry Non-Immigrant Type O-A (Long Stay) visa from a thai consulate in their country BEFORE they wing their way here.
Hands down it is the easiest thing to do. You don't bank a single baht in a thai bank account, you meet the financial requirements in YOUR country using your bank account or documentation from your govt.
That visa gives you almost 2 solid years of trouble free stay in thailand and you don't have to worry about ANY changes to the extension rules by the immigration office inside the country because you bought a VISA from a thai consulate outside the country BEFORE you came here..
Good Luck all.