Bangkok to Beijing to Tokyo

Hello,

I'm an American (U.S. passport holder) that will be attending a conference in Bangkok, Thailand this week, and when I leave there, I want to briefly visit China before heading to Japan. If I book a one-way flight from Bangkok to Beijing, stay a couple days in Beijing to see the city, then book another one-way flight from Beijing to Tokyo, am I eligible for the 72-hour exemption?

Thanks,
Jeff