@Daniel ****
>no need of a statement saying the money was on the account for two months ?
TO get a one year extension of stay based on retirement, you need a letter showing the 800K THB was in the bank for two months BEFORE you applied, AND 3 months AFTER your last extension of stay was granted, AND the amount of money never fall below 400K THB during the in-between period.
>Copy of the bank book to be added to the letter
You will need a bank book, updated the same day, that shows the money is in the bank. Add or subtract about 100THB so it'll show up.