the rules are pretty cut and dry, the enforcement is definitely not. Regardless cash has been the requirement. He needs to hit the ATM, because he could be asked to show cash when he arrives in Thailand
You will get mixed reviews on all, but the big 3 mentioned are probably the best bet. If you are using it to keep the 800k baht for a visa, Bangkok bank requires freezing the 800k for 4 months now. Not sure if the others will follow their lead. I have been using Bangkok Bank without any problems. Don't have personal experience with the others
banking in Thailand is going through big changes. Everyone just needs to weather the storm. It's going to be more difficult and confusing until they get everything lined out. Anyone expecting clarity or continuity is going to be greatly disappointed for a while.