Hi, we are couple afrom Czech Republic travelling from Thai to China

and back home to Czech Republic. We would like to stay in Shanghai and Suzhou (Jiangsu province) from 6th June till 12th June (hope I count well the hours and days). However, I´v heard there might be some issues on the airports as we won´t have a visas in our passports. Is there any official document which we can show on the Thai and China airports and make the passport and visa check easier?

Thank you so much for any help
Anezka