I'm an English teacher on a Non-Immigrant B visa. If I don't get screwed over by the school, come May time I may be looking at three months paid holiday, due to the shift to ASEAN. If I accept a job in China for this period, can I apply for a Chinese Z visa (work visa) without affecting my Non-B visa or would it automatically get cancelled out? If I can keep the validity of it, then as long as I get a re-entry permit could I go and do a few months work in China and then return in time for the new term? I don't want to tell the language school in China that I don't intend to stay for the full length of the contract, and that I actually plan to return to my job in Thailand. Can I get away with it?....Or am I being very dumb and naive about it all? Also how long is a re-entry permit valid for? Thanks

Whatever the answer is to the visa question ----- consideration should be given to the ethics of what is being planned.

You seem to be on an extension of stay for employment. As your employment is not being terminated (paid leave) your extension of stay remains valid and your re-entry permit will be valid for a return trip to Thailand within that date. Any visa to travel to another country has no effect on your permission to stay in Thailand.