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
the airlines bother, simply because if immigration refuses your entry, the airline is, by law (!) responsible to carry you back to the port of origin at their own expenses. And the airline will get fined by the IATA for 10.000.- US$
Savannakhet changed their requirements as of lately. You now need the 400,000.- THB financial proof for the multi entry Non-Imm-O family. However you can get the 90-days single entry Non-imm-O Family visa without the financial proof
if you fly Finnair out of Helsinki, they will not ask anybody for an onward travel proof - until now! My friend flew out from there without a visa 5 weeks ago. However they might do so in the near future, should they ever have to return a passenger whose entry into Thailand got refused, because it will cost them 10.000.- US Dollar in fines