Return flight passes through Shanghai

I am an American with a US passport. In November, I travel to Shanghai for 3 days in order to give an academic lecture. Then I leave via the same airport to Thailand in order to lecture there for four days. Thus I should qualify for the 144 hours TWOV program while in Shanghai. However, when I return to the US from Thailand, my flight passes through Shanghai, where I switch planes. I will not leave the airport, and the layover is only a few hours. My question is this: does this count as a 'double-entry' into China, which would invalidate the 144-TWOV rule? I've called the embassies each several times, but can get no answer. Thanks kindly!