Sabre lists the fare as unrestricted. If this is correct, the no-show fee is $0 and you can rebook your dates at no charge, but you must fly the SFO-YVR portion and there may no longer be availability on your original dates.
I have no-showed on full fare tickets plenty of times without problems but I don't have experience with these ex BKK fares so I may be wrong - anyone else feel free to chime in
Cheers