Nope. Can't check thru to Vancouver w/o new check in. Yes. Great idea. But. Now it is $2,000 return or +$650 from what we paid, I.e. $1350 each return.
We did checkin online, but it would only accept checkin from Thailand to Tokyo and not from Tokyo to Canada. Therefore in order to get Boarding Passes for both and get baggage on the plane, we had to line-up and recheck in to get to Tokyo and to Canada. Such is life!
We flew today with ThainAir/ Air Canada to Tokyo and then Vancouver. Our plane leftv at 7:30 am. We got to the airport just before 5. There was a big lineup at checkin. After that we breezed thru Security and had a good 1.5 hrs to spare. In summary 3 hours would give you a comfortable pace.