Visiting Beijing for 36 hours, but stop in Changsha

Hello,

I am flying from Bangkok to Beijing. I will only be in Beijing for around 36 hours for work. But I am worried because on the way to Beijing I have a flight from Bangkok to Changsha and then connect in Changsha to Beijing. On the way home my flight is direct.

So my question is - will they make me clear immigration in Changsha or can I connect through to Beijing? Because I'm worried that if I have to clear in Changsha then I might not qualify for the 'entry and exit through the same point' criteria given that I'll have enterd in Changsha and exit in Beijing (even though both are qualifying city).

Thanks