Thank you all for sharing your info re: O-A visa funds needed. I have one another Q. Where does one need to apply for a retirement visa -- in the home country (passport issuing country) or can I apply, let's say, via Thai Consulate in Vietnam or Laos or Malaysia?

Must I travel back to my home country in order to apply for a O-A (retirement) visa?

OA is only issued in home country or country of official residence. You can obtain a non immigrant O visa if over age 50 most places and during the 90 day entry apply for one year extension of stay for retirement at an immigration inside Thailand. This is probably what most people here on retirement do.