I've been burned too often ex-YOW.
I didn't want to be stressed before a vacation wondering if my Dash-8 to YUL will get out in time.
I could just imagine working with AC trying to get to Phuket if I miss my LX cnx in YUL. no thanks.
I'm 10* more confident that if things go wrong on YUL-ZRH on Swiss, they will get me to HKT in the class I'm booked (J) or better. The fact Swiss serves BKK with their own metal made it a no-brainer.

Routing is YUL-ZRH-BKK-HKT