Round trip flight Bangkok - Orlando through Shanghai PVG

Juan, your post is a bit confusing because you are mentioning certain refusal to be allowed boarding the plane, but you don't put it into a timeline that could be clear to the people that are trying to answer the questions.

Never mind, I will take into consideration your itinerary with two round trip tickets: Bangkok - Shanghai and Shanghai - Orlando. Indeed, when integrated into one logical itinerary, this two itineraries blend into Bangkok to Orlando round trip itinerary. First of all, this is definitely allowed and it was allowed since the very introduction of visa free transit policy in China.

You will print out your flight tickets and have those printouts with you. Also, you will declare at check-in in Bangkok that you will travel to US via Shanghai using 24 hour visa free transit. After a short inspection, you will be allowed to board the plane. Please, just arrive an hour or two before the usual time at Bangkok check-in because less informed and poorly trained airport staff could member could find herself/himself in a dilemma because of relatively specific combination of your flight tickets. If some problem occurs, you will kindly point her/him to take a look into Timatic and if this will not be enough, you should call a superior. In any case, you will be allowed boarding. Just invest an hour or two to arrive at check-in before.

Upon your arrival in Shanghai, you will be approach 24 hour visa free transit counter where you will apply for a temporary entry permit to be allowed to exit the airport or better to say to collect your luggage and perform new check-in for your flight to US. Basically, this is it and it should definitely function exactly as I have written.