I am looking for clarification and help about transit flight

Hi, i am holding Thai passport. I am looking for your help and clarification about my transit flights in Shanghai (PVG) and Nanjing (NKG) during my trip to Osaka on Apr 2017. I have 2 hrs. for fight transfering in PVG to KIK and on my return fight I have 4 hrs. to change the fight from NKG to BKK. Am I required to have transit visa on these port? Please help and thank you in advance.

Pat