If you want a special fare on CX you cannot combine airlines even OneWorld.

The way your routing is, unless your CX fare permits you to backtrack, you cannot do DPS and SIN or BKK.

CX flies from HKG direct to DPS. It doesn't stop anywhere else. So if you want to include DPS in this ticket, you'd have to split it.

USA-HKG-BKK-SIN-CGK (jakarta)
From CGK you buy oneway to DPS
Return DPS-HKG-USA

Don't know if you'd get a special fare for that.