Your employer, the school in Shenyang should obtain two documents for you and send them to you for work visa application:
1. Original Foreign Experts Working Permit issued by the State Administration of Foreign Experts Affaris
2. An invitation letter from the relevant department of the Chinese Government or Government-authorized company

If you get the above two documents, you should prepare the following documents:
1. One completely filled out visa application form. No item should be blank .

2. One recently taken 2X2 in. photo showing entire face and without a hat on. Please affix the photo to the application form.

3. Original passport with at least 2 blank visa pages and valid for at least 6 months beyond the date of application.

4. A Physical Examination Record for Foreigner filled out and signed by a doctor (together with their copies).

then submit them to the visa office of Chinese embassy/consulate in Thailand.