@Bob ******
and the short answer to that IS
IF you are using the 800K baht banked money as the method to meet the proof of funds at NO TIME can your balance drop below 400K during the previous year.
One last time, you need 800IK baht in your account for 2 months BEFORE you apply for the extension, it stays in the account for 3 months after you get the extension and then the balance can't go below 400K baht the rest of time time.