Def not enough if all you have is 500k baht savings. Because technically you need that in 6 months time for an extension. So what are you going to live off of? $100 a month? Impossible.
I don’t think you need 500k on every statement as long as you have it in the bank at the time of application and entry. The previous months statements are just to give a more detailed picture of your financial stability I believe.