Does a four leg itinerary qualify for 72 hour transit visa?

Does the following itinerary for a U.S. passport holder qualify for the 72 hour free transit in Shanghai? Should it be booked as 4 one-way tickets to qualify? Total time in Shanghai would be about 60 hours.

HKG --> BKK Depart evening of November 26th
BKK -->SIN Depart mid-morning of November 29th.
SIN --> PVG Depart mid-morning of December 1st.
PVG --> HKG Depart evening of December 3rd