Transit through shenzen

Yes, you are definitely eligible for 24 hour visa free transit and you do not need any kind of visa. I encourage you to use correct terminology because this is not 24 hour transit visa, but visa free transit, so there is no visa of any kind. If you plan to exit the airport, it will be very hard to accomplish that with 8 hours layover, but you can try it. So, if you want to try it, you will approach transit counter immediately upon landing where you will apply for a temporary entry permit by presenting your flight tickets. This application is free of any charge. If you are successful and a permit is granted, you will fill out arrival/departure card and proceed toward immigration in order to explore the city for some time. If the officials decide not to grant you a permit, you will remain airside waiting for your onward flight to Thailand. In any case, you do not need any visa.