What type of visa can my wife apply for to join me in Thailand on a retirement visa?

Your wife could always apply for a retirement visa herself in Thailand….

It might be worth your wife contacting one of the Thai visa processing centres while she is still in India and asking them for a definitive answer.

Sadly, (for your wife) at most thai consulates NO she cannot apply for a 90 day Non-O visa based on marriage to a foreigner here on a 'retirement visa' 😕 . AND even worse once she gets here she also cannot apply for that visa in country..

At this time there is no visa she can go on that will let her piggy back (be trailing spouse) with you on a retirement visa.

Now on the rare chance you got an OA Long Stay visa from a thai consulate in YOUR country before you came to thailand (the visa that requires a police background check, a medical certificate, and 100K USD in medical insurance) she MIGHT be able to get a 90 day single entry Non-O from a thai consulate with you on that visa..

Other than that (as in if you got your 'retirement visa' issued inside thailand there are little to no options) 🙁 Sorry about that, she'd have to find a visa that lets her stay which has nothing to do with yours