I used the combination method for a few years... I'm from NZ, my pension was only about 40,000baht month.. So I also had to go to NZ embassy and get a letter to verify my income From NZ pension.
I kept over 400,000 baht in my BKK bank.
After several years... I found this a major problem, trying to renew extension each year..
So now, I just keep 800,000+ in the account, at ALL times..
It makes life much much. Easier.