so use the proof of income of 40.000 THB per month instead. Either with an income letter from your embassy or a bank statement with 12 monthly transfers before you apply for the 12 months
in Thailand your wise card will be handled like an international card and get a 220 THB fee. Beside that wise isn't cheap if you want more than limited cash in a month....
Short answer no. You need to keep the 800kthb in the account. So don't spend it.
Your option, if this is your budget, is to rent and then you can use the 800kthb after you have switched in one year.... Remember that the 800 kthb is for that first year...
that is what I did too. Had a non o a and immigration recommendations was to kill that by going to Malaysia and return on a extemt and convert that when I got back