okay, first off
@Man****
, none of the financial stuff has anything to do with your 90 day reporting.
IF you use an immigration office that requires you to come back 3 months after you got your extension they will give you a piece of paper that states the date you need to update your bank book and show back up.
MOST <- as in all but a few offices DO NOT do this, and they now require the previous 12 months of bank balances when you get your next yearly extension and will look back at that time to see if you kept the 800K baht in the bank 3 months after your preivious extension was granted and then never let the balance go below 400K baht the rest of the year.
This is what that "come back in 3 months" paper looks like