All I know is that I was told by UOB that the only requirement to release funds upon death to a named beneficiary on a UOB account is that the beneficiary needs to present a copy of their Thai ID card and the death certificate. You may want to check with UOB directly for further clarification if you doubt this to be correct.
I don't need to check with UOB, unless your account is a joint account the information they have given you is incorrect, UOB (as do you) may want to check the Thai administration/'probate' law, then your beneficiary doesn't risk disappointment after your demise. Banks are not permitted to circumvent 'probate' law as far as sole accounts are concerned.