Seeing as you want Bangkok, I'd bet on Thai Airways flights. But you're going to have to do some research as to which airlines typically offer the lowest fare to BKK with the number of connections you'd be comfortable with. I'm only really familiar with OneWorld and I know there you could do Cathay SFO-HKG and then HKG-BKK.
From what I've heard, the Asian carrier's loyalty programs are not as generous as US Carriers (and even those are de-valuing). What are you looking for in a loyalty program?