Maybe not possible anymore, but i did following: went to immi after i had my non imm O and they made a letter for BKK bank to open an account.( Hua Hin, small office at first floor, 500 baht)
i use both, app and online bkk bank, is safe, and online you can only transfer to existing contacts/ accounts... for new one u need to confirm with OTP send to your phone...