get the O-A retirement visa before you leave, needs proof of funds, medical cert, police clearance certificate and health insurance (Axa offer a good product here reasonably priced, designed for visa purposes - has a high excess/deductible so not ridiculously expensive)
Joint accounts here are a pain, we tried it with BKK bank, could not get online banking despite them telling us it was ok, and anytime you need anything done you both have to trek down to the branch - moved to individual accounts with SCB and a pleasure to deal with and good on line app……..
Probably best to leave and come back with the correct long term visa, only a matter of time before you get stopped and refused entry, for gaming the system.
that’s part of the game, banks and immig especially, make life challenging in order to drive impatient people towards agents, nice pay day for them - DLT is doing the same since Covid - encountered this for 20 years working across Africa……