A couple of points - in case you don't know. Note that once you have an OA , the only way to switch to an O (that i am aware of) , unless things have changed, is at some point you will need to depart Thailand, without a re-entry permit associated with the OA and in effect 'kill' the OA. This means you must depart Thailand after the OA visa 'valid' date but while still on a permission to stay in Thailand associated with the underlying type-OA. (I hope I have my terminology correct). That's what I ultimately did some years ago. I was on a Type-OA extension, I left with no re-entry permit (which invalidated my Type-OA), and returned to Thailand Visa exempt. I already had the needed funds in a Thai bank and so as soon as I returned Visa exempt to Thailand, i applied at local immigration for a 90-day Type-O. Once I had that, with about 45-days left in the 90-day permission to stay in Thailand (that comes with the 90-day Type-O), I applied at the same immigration office for a 1 year extension on the permission to stay (based on retirement) on that 90-day type-O visa. For some Thai provinces i think 30-days before permission to stay in Thailand expires, is the number instead of 45 days in which one can apply. Just a heads up on this, as I think it has not changed over the years. Using your non-Thai health insurance to get a Type-OA while outside of Thailand can work - and likely did for you. But ... but ... But once inside Thailand, if you ever wish at some point to get a 1-year extension that goes past the duration of the permission to stay associated with your Type-OA, you will not be able to use your non-Thai branch health insurance. You would (for a 1-year extension on an underlying Type-OA) have to go with health insurance from the Thai branch of a health insurance company. That was a show stopper for some of us on Type-OA visas (as our foreign health insurance was too good to give up , and we did not want to buy double health insurance). Hence many of us left Thailand, to 'kill' our Type-OA, and switched to the Type-O - which I believe is Dr.Jack54's point in suggesting Type-O. Possibly you are already aware of all of this -and if so, my apologies for 'spamming' on this aspect.
