I don’t understand. If you have 800,000 in the bank you can continue to use it for each year extension. If you are trying to switch to the monthly method you can wire transfer a monthly deposit.
Whatever works for your IO office is what you should do. It varies from office to office. Getting a bank statement is pretty easy. I'm not sure why there is resistance to getting them but . . . up to you
I keep 800,000 baht in my Thai bank year after year because it is simple to do and I can afford to do it. I don’t have to track whether I made a deposit each month and more importantly whether each deposit is tagged as a foreign transfer. I never have to think about meeting the financial requirements. I think the key factor here is that some of us can afford to keep the money “tied up” and we consider the monthly method too much of a hassle.
They are just pages printed by the bank. Nothing complicated about it. That is what staples are for. It is true though that there is less chance of accidentally dipping the balance too low. Never been a problem for me.
A bankbook is not a reliable statement of the year banking activity. I literally never update my bankbook except on the day of my extension application.