Nepal to Tibet to Yunnan

I'd like to travel from Kathmandu to Tibet, and then continue into the mainland this July on a tourist visa. From Nepal to Tibet, I'm hoping to take the friendship highway, and then fly from Lhasa to Kunming. Is it possible to get the requirements in Kathmandu to do this? From my research, it seems that I can get a travel permit from Nepal to Tibet, but I'm not sure if this permit includes mainland travel.

Any advice or recommendations?
P.s. I have a Canadian passport.