Can you obtain a retirement visa for Thailand from a third-party country?

@Terry ****

There is no such thing a “retirement” visa. You can get a visa based on being over 50 years of age.

A non immigrant O visa is valid for 90 days and would give you 90 days on entry.

A non immigrant OA visa is valid for one year. It’s a multiple entry visa so you can come and go as many times as you like during that year. Each entry would give you 365 days stay, providing you have health insurance for that period.