Do I need to take Guangzhou visa in this case?

I hold ordinary Indian Passport, we have VOA in Thailand and in Hongkong. If I am traveling, I plan to travel to Gaunzou from hongkong by train.& will also return to Hongkong by Train. We have VOA in Hongkong.We will be In Guangzhou to see Export Exhibition and will be three days. Also what If I am travelling to Gaunzhau from Bangok, where I have VOA facility?
Pl. inform, thanks.