Thai Immigration has absolutely nothing to do with this question, it can only be found on the Thai customs webpage. And there sadly is no information to be found regarding currency import. It can only be found on SOME embassy websites
with more than 800,000.- THB in your bank account, you should experience no difficulties to get the bank letter for two months seasoning in order to prove the financial requirements
doesn't the bank print "condensed transfers" in and out of the account? As a summary? your problem is: for the applications you need a bank proof of 12 months, month for month, showing incoming from abroad minimum of 65,000.- THB. If you miss out only ONE month, your application won't go through. You would be better of with the 800,000.- THB in your account, it would be as easy as it is peasy