THAILAND to MEXİCO via Guangzhou -CHINA (18 hour 20 minutes)

To Whom It May Concern

I would like to buy ticket from some company as follows: THAİLAND to MEXİCO via Guangzhou -CHINA (18 hour 20minute). China Southern Airlines
But I don't know do I need transit visa or I don't need ? I am citizen of Turkey.

Waiting your soonest reply.

Best Regards