@Wayne *********
you need a print out from the bank showing the international transfers each month every month for the previous 12 months that are at least 40K baht AND you need the regular bank letter from the bank that lists your account number, your name and the balance of the account on the date you got the letter AND you need to update your bank book on the date you apply.
Some banks can print a year's worth of international incoming transfers separately BUT some cannot and in that case you need a printed stamped copy of ALL the transaction history for the previous 12 months. You should highlight the incoming transfers for them if you have to get that.