Most of my assets are in investments. In north America, my attorney advised me to forgo the will & testament and just set up the beneficiary on the investment accounts. Apparently this overrides any will and would not be accessible to any unscrupulous siblings, ex-wives, etc. Not sure what the rules are here for this sort of thing. 

I bank at Ayudyha (Krungsri) bank, so I don't know if this would apply to Bangkok Bank, but I have the account in my name only, but I've authorized my wife to be able to do transactions using the bank book. She could take my bank book down and withdraw the money on her signature and ID. I did this for the very reason you're citing: if I was incapacitated or dead.