@Susan *******
That is what I did. I kept 800,000฿ in the bank + a couple of 100,000฿ emergency buffer and then topped off the account with my monthly expense money. The buffer keeps you from accidentally dipping into the 800,000฿. This way you can use just one bank account. Often people get a separate bank account for the 800,00฿ to protect it from monthly expense accidents. That’s OK but I sounds like it is a chore to get a bank account these days for new arrivals.
Note that yearly extensions for the O and OA are identical except for the OA insurance requirement. The 800,000฿ deposit is the same for both visas. As I recommended earlier, you might as well get an O and deal with insurance separately.