My wife has just switched we arrived a year ago on non O 800k . She had to show 12 deposits of 65k + with a letter from the bank confirming the deposits . They were insistent on this . Hope this helps obviously this is our experience in Chiang Mai .
We moved over last year from the UK . And both had to apply for a Non O individually. Then both opened bank acc on arrival and deposited the 800.000 we are currently changing my wife’s over to banked 65,000 a month .