Once you get an account at a branch then that is your branch. I got my Kasikorn account at a BKK branch. Then I moved outside Bangkok. I couldn’t just move the account to my countryside branch. I even had to come to Bangkok to close the account
My pensioner LTR was a long time ago (2023) but yes, they continued to ask for more documents. In my case they wanted copies of additional pages in my passport. The email back & forth will add a few more days to your wait time.
Mostly what I’ve heard is that they are getting a better rate of return on the $23,700 in their home accounts and that they don’t trust Thai banks. Everyone has their wants and needs.
I’ve heard that some people do that. I didn’t do that because I live in Thailand full time. I would never be in the US long enough to complete the OA application process which is a bit of a pain. It’s a peculiar visa and some people benefit from the peculiarities.
It also benefits people that don’t want to open a Thai bank account because you can keep applying using funds in your home country bank.
I did get 18 months on my OA visa because of a trip to Cambodia but I really didn’t care about the extra months. Yearly extensions is where most people want to be.
That is what I did. I kept 800,000฿ in the bank + a couple of 100,000฿ emergency buffer and then topped off the account with my monthly expense money. The buffer keeps you from accidentally dipping into the 800,000฿. This way you can use just one bank account. Often people get a separate bank account for the 800,00฿ to protect it from monthly expense accidents. That’s OK but I sounds like it is a chore to get a bank account these days for new arrivals.
Note that yearly extensions for the O and OA are identical except for the OA insurance requirement. The 800,000฿ deposit is the same for both visas. As I recommended earlier, you might as well get an O and deal with insurance separately.