Tough time to get a reward flight for the outbound leg. Are you flexible with dates at all?
I'd definitely encourage going for business class. Economy that distance will be very painful, and the real value for your points is in business class.
There's availability from YYZ/YOW to LHR to FRA to BKK (with AC, LH, TG), but that's going to cost a fortune in taxes ($800+ fuel surcharge alone).