What are the requirements for obtaining a retirement visa in Thailand if I am already in the country?

Just checking how your trip to apply for your 90 day Non-O visa went today

In Bangkok this is where you go

For an in country Non-O you don't need a police background check or a medical certificate.

You will need your lease, probably the condo owners thai i/d and the house book listing for the place you rent, BUT that's just a guess from seeing people need it when applying for that Non-O visa in country.

I'd go out to the immigration office and ask for the hand out at section C-1 which goes over everything you need to supply document wise.

To answer your question NO you're not gonna get a 'retirement visa' out at chaengwattana when you go

The way it works IS

you need 15 days left on your current stamp to apply for a 90 day Non-Immigrant Type O visa based on being over 50. The reason you need that is because it goes under consideration for 14 days before you go back and get the 90 day Non-O visa inked into your passport.

THEN you wait until you have 45 days or less left on that new 90 day Non-O visa and you go apply for a yearly extension.

You apply for your 90 day Non-O visa in section C-1 out at the immigration office at Chaengwattana. It costs 2000baht

When you go back to apply for the year extension you do that in section L and it costs 1900baht

you are confusing the requirements for a year-long, multi-entry Non-Immigrant Type O-A (Long Stay) visa from a thai consulate in your country with the requirements for a 90 days Non-O visa and then a yearly extension from the immigration office inside the country. They are completely different.

What visa are you on now??