I’m not sure how when you fly out and back again the officer will care about conditions of visa acceptance, they never ask if you still have 800k in the bank for retirement visa. You have valid visa, stamp and enjoy your stay
but the 800k you need to leave in Thailand earning zero, can earn 5% at call in Australia and the yearly immigration visit is very draining even if it is straight forward, I’ll get DTV next time, already moved my 800k back home
The tax years are calendar years here. Jan-Dec, can do 3 months to Oct-December and leave before March ends and that’s not tax resident, though nothing has been confirmed as above about tax