that could mean you can come and go during your one stay. That would mean purchasing a DTV every year and pay 10,000 baht twice every year. Again, we don't know. Assuming that is what a multi entry visa means is just dangerous without more information.
no one knows if you are allowed one 180 day stay every year or if it is one with an extension available in a 5 year period. We need to know more about it.
Still need more information on this. No one is sure if you can come every year for 180 days or if it is a one time use within a 5 year period. If the latter, some folks will be screwed because they think it's the former.
BRICS is not the threat people tend to think it is, for starters, and Thailand really doesn't want to fracture what is called the "special relationship" it has with the US. I wouldn't worry at all.
don't worry. You're fine with Navy Federal. I use Schwab and Fidelity who are also fine with an overseas address (outside black listed and some gray listed countries, of course, but no danger of that in Thailand.)
as far as banking, the best advice is to use an institution, like Schwab, Fidelity, Navy Federal, etc. that allow an overseas address. I've moved everything to Schwab and Fidelity.