Also, CX does not seem to release that many seats to One World. I don't know about a single first class seat SFO-BKK, which seems to be the OP's objective, but I do know I have not been able to fine a single Y class redemption for HKG-LAX for either June, July or December.
So I would caution the OP to not get his hopes up too much and have alternate plans in mind. ALternately, if you really want CX, then accumulate all the miles onto CX...