Do aircraft even have the range to do YYZ - BKK non-stop? YVR - BKK is likely do-able though.
I concur that Thailand overall tends to be vacation-centric for Canadians. I don't believe there's a lot of business travel there like there is with LHR / FRA / HKG for example. Furthermore, I'm not sure that BKK is really a final destination for vacationers versus say HKT or CNX.