The best value for singapore to Bali is, IMHO, KLM. $415 round-trip in international business class.

https://www.google.com/flights/#search;f=SIN;t=DPS;d=2017-01-06;r=2017-01-08;sel=SINDPS0KL835,DPSSIN0KL836;sc=b

Plus if you're leaving on the 6am UA flight to HKG, the KLM flight lands at midnight. So you can book the air-side transit hotel for six hour and get some sleep there or couch surf in a lounge.

The KLM flight might spoil you if your long haul flights are in Y though.