Where to go after Hong Kong??
 

I'll be traveling for two weeks through Asia in May, staying ~3 days in Beijing, Shanghai,& HK.
I want to spend an additional 10 days in the region, but I would love some recommendations to go after in East/SE Asia.
I've already visited Singapore, Malaysia and Bangkok already!

Three days is very short for Beijing. If you've gone to the trouble of getting a visa for China I would spend more time there - maybe Xi'an and Chengdu, or Chengdu and the Kunming area. Or you could go to Taiwan - more history and less pollution than the mainland, along with good scenery.

I'd agree, stay in China.