Can I bring my wife and daughter to China on my residence permit?

Hello,
I am an English teacher in China and have just come into China on a Z visa which is currently being converted into a foreign expert certificate/residence permit by my employer.
What is the easiest way to bring my wife and daughter from Thailand?
Is it correct that I need an invitation letter from my school, and then we apply for a Z at the Chinese consulate in China for my wife and daughter? Many thanks for your reply.