They know the visa when you opened the account, and at some stage you have to go to the branch to carry out some transaction and that's when they see if you've changed visas. Bangkok Bank are randomly selecting people to take their documents into the bank for checking. I'm expecting the other banks to do the same. The banks are no longer maintaining accounts for tourists
Possibly not. I went from non-O to DTV and Kasikorn Bank has given me six months to change visas or they will close the account. Bangkok Bank are a bit more abrupt. They are freezing many accounts without warning and requesting the account holder attend their branch with required documents
You're on a tourist visa so yes you can drive on your home country licence with an IDP. As a temporary visitor you can drive up to the expiry date of your entry stamp. You will get experts telling you it's 90 days maximum which is total BS. Enjoy your stay!