When we got married thirty six years ago my wife told me to never get into an argument with a Thai. Leave it to her. Very good advice. Argument and reason is not at the top of many Thais lists of attributes. It can make you an enemy for life.
Not to labour too fine a point, but can an instruction to the bank be made to insert a clause in your account stating that your lawful wife will be able to have access to it on the production of a death certificate?
This raises the question of the Bt800.000 deposited in a fixed account for visa purposes. If the the holder dies can his legitimate spouse withdraw it on production of a Thai death certificate or withdraw it with the ATM card? Should she report her spouse's death to the bank?