Bikhub will not open accounts for US citizens (ay least nkt any more). SatangPro will but account opening takes forever and endlesd papereork to submit).
Strange I have a Kasikorn savings account and I get paid interest (twice a year June and Dec). But rate is very low so as others say best ti leave the money overseas if you want interest for it.
My wife is an insurance agent in Thailand and unfortunately no Thai health insurance companies will cover preexisting conditions. All you couls do is to apply and see exactly what they will exclude when they evaluate your application. The Thai companies will generally be cheaper than the international ones. Good luck.