Depends whether you're leaning towards *A or OW. As far as convenient routing goes I'd be tempted to look at CX out of JFK or EWR direct to HKG and then connecting to SIN. CX have an excellent business class that I'd be more than happy to take on a flight of that length.

Otherwise a lesser and probably less popular option would be UA direct EWR-HKG if you were chasing *A. I've taken that flight though and honestly didn't mind UA business