Standard Mandarin is the official national language of China.
Chinese is spoken by the Han majority and many other ethnic groups in China. Nearly 1.2 billion people (around 16% of the world's population)
There is some different between Thai languange and Chinese languange in many ways such as speaking and writing. These can lean to conversations problem. Most of Chinese people can not speak English. They can only speak their own language. When you visit China these kind of problem will occur for sure.