What documents do I need to change my retirement visa extension to a marriage extension while switching banks in Thailand?

I am doubtful that just updating the passbook on the old account will show the transaction history enough to meet the requirements

Remember you have to show that you kept the 800K baht in the account for 3 months after the extension you're on now was granted (last year) SO you would need to have the year detail transaction print out for that account and probably also update the bank book the day you apply

AND

as you're switching banks to use another one for the new marriage extension you'll also need the 3 month statement for that account, updated bank book the day you apply and the bank letter