I have a one-way saver ticket from Shenzhen (SZX) - Beijing (PEK) on Air China for 15,000 miles.

I was thinking of changing it to

Shenzhen (SZX) - Beijing (PEK)
Beijing (PEK) - Kunming (KMG)
Kunming (KMG) - Kathmandu (KTM)

Would this be a valid routing? Open-Jaw return with one stopover or am I being a bit too optimistic? In my head it made sense but looking at it now, I really don't think it's legit!