What visa should my uncle apply for to stay in Thailand for a year on retirement?

Hands down the year-long, multi-entry O-A visa from his country before he wings his way here is the way to go. (y)

It can't even be compared to a 90 day Non-Immigrant Type O visa and then a yearly extension of stay you get inside the country at the immigration office.

I'd say tell him to NOT be lazy and get the O-A from a thai consulate BEFORE he comes here. He'll be set to come in and out of thailand all he wants for a year and he can get 2 years of stay out of it.

Scott - in the sense that an age 50 or older person can stay in Thailand for a year, - the AO Visa is similar to getting a One Year Extension of Stay to Non Imm. O Visa. But you obtain the OA differently and the OA is more generous in benefits. As already said you get the OA visa at a Thai Consulate / Embassy in the home country... You prove possessing financial ability in home country currency equivalent to 800,000 Baht, a police check and medical cert. Plus the visa fee. On the face of it the OA visa is good for one year. But an exit from Thailand and reentry just a day or two just before the first year expiry grants another year's stay from the reentry date. Being Multi-Entry in the first year the OA Visa also allows unlimited exits from Thailand and Reentry which can allow for easy regional tourism. In my opinion the OA visa is the best choice for folks age 50 and over.

You buy the Non Immigrant O-A Visa at the Thai Embassy in your home country, this Visa will give you during the 1 year validity 1 year of stay at each entry till the Enter Before/Valid Until date on the Visa. The Extension of Stay based on being over 50 years of age, has as requirements the Non Immigrant O visa, money in a Thai Bank or income certified by Embassy. It is not the same.