I am also an Oneworld person, so I travel mostly on AA/CX for that matter.

I would recommend you do BOS-JFK on AA, JFK-YVR-HKG-BKK on CX on the outbound, where you can stopoever in HKG for free. On the inbound, return from SIN-HKG-YVR-JFK on CX, then JFK-BOS on AA. The trans-Pacific can easily be issued as an open-jaw, while the RT BKK-HKT tickets can be had for a mere $160 in biz class on TG, and for the one-way BKK-SIN you can do AY (on M, W, F, Su) for $150 in biz or LX (daily) for also $150 in biz. AY segments count for elite status in Oneworld! LX earns AA miles.

Interestingly i am leaving for the exact same trip next week. I am doing the following:

11/14 SFO-JFK AA
11/16 JFK-YVR-HKG CX
11/22 HKG-BKK CX
11/26 BKK-HKT TG
11/29 HKT-BKK TG
11/29 BKK-SIN LX
12/01 SIN-HKG CX
12/01 HKG-SFO CX

I beleive this is the easiest and cheapest alternative you can find, with options to visit all the aforementioned places.