Two things have to be correct with K-bank: 1. Registered phone number name/passport number has to match the registered bank account. 2. You need to go to a branch for a face scan.
Aha, okay. A bit off topic but I even read that someone only could get a 2 year drivers license because he only had 3 months left on his current year extension. Although he lived here for many many years on year extensions.
I also think y'r okay. I mean this is what a 'normal tourist' would/can do. On top of that you did not ask for a 30 day extension so far. Be sure you have the 3 proofs. (20k฿ or equivalent in cash, place to stay and onwards travel outside Thailand).
For the non O it's not mandatory. But, of course it's always good to have one. First I would contact y'r home insurance if and how long you are covered abroad .