I find that partner awards are best done by phone with BAEC, especially if you want to take advantage of enroute stopovers (not possible online).
I'd advise that you consider a JFK - HKG - BKK routing on CX in J (100K BAEC miles per person), and then work out separately the HKG - TPE trip (either cash or use either BA or AA miles for CX seats) and the BKK to Cambodia/VietNam/Laos legs.