U.S citizen and I Fly on 10 Nov 2016 from Los Angeles To HK with a 2 hour layover in Beijing

I will arrive to Hong Kong on 11 Nov 2016 at 11:25 am and leave to Bangkok 14 Nov 10:45 am.

And the way back on the 26 nov 2016 I Fly from Bangkok to Los angeles with a 20 hour layover in Beijing ., and was planing on leaving the airport to stay the night in a hotel and then coming back for my next flight.

What kind of visa do I need?