Open at a BKK closest to where you live. Is not like in USA where you can always go to any branch. Many things you can only do at your "home" branch. Especially true if you intend to live in Bangkok. The Bangkok branches are kind of separate. Also there is a branch of Bangkok bank in New York City
I never once did a TM 30 in my three years in Thailand. I thought landlords and hotels took care of it. I have stayed in a few places where they did not even ask for my ID. Never had a problem with the 90 day check in