@Holger *************
Any foreign Last Will is NOT valid in Thailand. For all your assets in Thailand, you need to set up a Thai Last Will, according to the Thai Civil Code
And even when you name a beneficiary and executor in your Thai Last Will, it first needs to go through a Thai Court. Only by the Court order, your bank account will be released.
KEEP IN MIND: Any person who withdraws money at the ATM from an account that was set up in your sole name, after your demise, is acting illegally and can get prosecuted!
It could take up to 6 months until the Court clearance, and if the beneficiary is not your Thai wife, the person you named as the beneficiary could get approached by a court staff and asked to pay tea money first.
Keep in mind, corruption is widespread