Do my wife and I need to apply separately for a Thai retirement visa, or can we apply together with a joint bank deposit?

@Vari ******

whether you can or can't use a joint account to get the extension based on retirement after you're here is totally up to the immigration office you deal with, SOME will let you use a joint account with double the money in it (1.6 mill) but some will not, SO I'd say once you get here GO to your immigration office and talk to them.