It seems to depend on the individual branch, not on the bank itself. I opened an account absolutely hassle free at KBank in Sri Racha (on the advice of an Immigration Officer in Sri Racha)
I do mine in Sri Racha, which is rarely busy anyway, so I'll leave it for a while. I would think the clock on the next 90 days starts as soon as you do this one - it might save me a visit in the long term if the amnesty is extended again. :)
As Stan said, a better option than METV would be an ED visa. Tourist visas in any country are not designed for long stay "visitors" and repeated METVs indicate to Immigration that you are not a genuine tourist.