Listen to what Sinned is saying. China is a PIA for bikes, but doable if you take the time and effort. And if you do, it is probably very rewarding. Inner Mongolia, Tibet, etc all look awesome. But again, PIA, requiring special permits, etc.
For Fly and Ride options;
-Chiang Mai, Thailand - it's cheap, straight forward. All the rental places in CM seem to be legit. But the riding in the area is nothing special IMO. Mae Hong Son loop is just OK, but it really depends where you're coming from. It's still a good ride if you can jump on the plane and get to CM quickly and cheaply.
-Vietnam - North Vietnam looks great. Easy and cheap rentals.
-Laos and Cambodia- easy and cheap rentals. There are some dirt bike outfits.
-Leh, India - This is by far the best riding you will do, ever. It's not just good for the region, it's amazing compared to anywhere in the world.
-Katmandu, Nepal - easy and cheap rentals. Probably 2nd best after Leh.
Now that I think about it, almost every country going South and East has something going on and it's usually cheap and easy. Malaysia, Indonesia, Philippines, Sri Lanka - almost everyone seems to have some cheap moto rental and cheap accommodations perfect for a moto trip. Do any of them for a short ride, and save Leh and Katmandu for a long ride, IMO.