My flight from Thailand to stop over at Changdu , can i got 24 hrs TWOV?

Thai citizens are eligible for 24 hour visa free transit. They are not excluded from it. Your itinerary and you are definitely eligible for 24 hour visa free transit and you don't need any kind of visa.

You will print out your flight tickets and have those printouts with you. Also, you will declare at check-in in Thailand that you will travel to Chicago via Chengdu using 24 hour visa free transit. After a short inspection of your tickets, you will be allowed to board the plane. If you encounter an inexperienced member of the airport staff, you will politely tell her/him to make an insight in Timatic and if necessary, you will ask for a superior because you are eligible. You will obviously travel on separate tickets and this is fine and acceptable.

Upon arrival in Chengdu, you will immediately approach 24 hour visa free transit counter where you will apply for a temporary entry permit. It will be definitely granted to you because you will have to collect your luggage and perform a recheck for your flight to Chicago. Also, you can explore a city for a short time to see some of the attractions or simply to have a good meal before the continuation of your journey to Chicago.

Thank you very much for your kind advise.