24 hours stop over in shanghai after visiting thailand

Hi, I am currently in China on an F type. I will be in shanghai on the 21st of August and I will have used up my maximum number of entries into china.

I do not fly back to the UK until september 5th. So, I was wondering if I could fly to Thailand on August 21st from Shanghai, and then return to Shanghai on September 4th, to fly out back to UK on September 5th.

Would I be able to do this, with the 72 hour period, especially because I will have used up all my entries into PRC?

Only problem I found was I would fly to Thailand from PVG, and return to PVG, but when I leave china on september 5th, I would be leaving from SHA. Is this a problem?

Also, hate to be awkward, but could I potentially travel around, i.e. fly shanghai - bangkok - indonesia - cambodia - shanhai - UK.... not that I plan to do this, but I mean does the flight have to be shanghai-bangkok-shanghai? or Can I fly in and out from any airport? BTW, I have a British passport.
Regards.