In this case, I would do an open jaw or 2 one ways to take advantage of the 15% discount. The option for stopover(s) in SIN/NRT/SFO/HKG/DME/FRA should also be available to you and depending on how you ticket it you may even save some money. However, you will need a phone agent to help you with ticketing this.
XXX - SIN - NRT/SFO/HKG - West Coast
East Coast/IAH - DME/FRA - SIN - XXX