Why Google keyboard doesn't have Chinese key board in side?

[spracha]

hello friends, I need to use 3 languages with my phone which are English Chinese Thai. Now I installed the Google keyboard in the Mi3 stable Rom to have Thai keyboard and english keyboard in the same apps but surprisingly I cannot have Chinese in the Google key board, I should use another apps "Google pinyin" to type Chinese that means I have to switch 2 apps all the time, it is ok but not smooth.
So I would like to know if there is a way to have Chinese pinyin in Google keyboard apps. Thank you (This forum is very useful).