And one more wrinkle:

Not sure when you are flying, but UA just announce a new SFO-SIN route.

Sometimes they have special fares when a new route is announced.

Lots of LCCs on SIN-BKK on that short hop, and lots of carriers including UA on LAX-SFO.

Just another option. For one stop, EVA would be hard to beat though, as has been mentioned.