I keep reading about challenges getting awards in Cathay's Business Class but from YYZ it's not a problem. So if you have a way to get to Toronto to start your adventure, keep it in mind as an alternative. Whenever I've wanted YYZ-BKK-YYZ in Business on Cathay, I've called AAdvantage (even before I had high stAAtus) and "poof" it was done. I strongly recommend Cathay's J to Asia.
Enjoy Angkor!