What are the requirements and process for obtaining a Non-O retirement visa while in Thailand on a visa-exempt entry?

1 - SOME offices (Jomtien specifically) DO require the 800K baht to be seasoned in a thai bank account in your name only for the 2 months before you apply for the initial 90 day Non-O visa

BUT

Some offices (bangkok for example) do NOT require it to be seasoned, just transferred in to a thai bank acount in your name only from abroad

2 - nope, banked money method always has to be 800K baht in a thai bank account in your name only (unless you come from a country whose embassy here issues the affidavit of income from abroad notary letter).

3 - you put on your big boy pants, get out there and pound the pavement hitting branch after branch asking if you can open an account or not. It will take close to a dozen tries but you WILL be successful in the end. It's just a numbers game and if you hit enough bank branches you'll find one that will let you open an account

4 - you could go to the thai consulate show proof of funds in your foreign bank account and possibly get a 90 day single entry Non-O based on being over 50 (retirement).

unfortunately it won't help all that much, because you're not gonna get a yearly extension inside the country at the immigration office without banking the 800K baht in funds for 2 months before you apply for the extension 😕

There just are so few reports since covid 'ended' and the consulates/countries opened back up about it that I'd say look at the website of the consulate you're thinking of using, meet those requirements and go try it.