Kunming Training Seminar， can we enjoy the 72 hour visa-free transit?

Hi,
A colleague and I are flying from Bangkok, Thailand to Kunming, China for a training seminar. I am an American, and he is an Australian.

We will have round trip tickets from Bangkok to Kunming already purchased before the visit. However, we are flying from Thailand to China, and then back to Thailand. Are we still eligible for the 72-hour wavier?

Thanks for your help!