M Visa extension

Generally speaking, you need to go to the local Exit-Entry Adminstration Bureau to apply for a extension with your valid passport, application form with recent taken photo, Temporary Residence Registration Form, your inviter's business license or other legal registration certificate, an introduction from the company sealed by the local Exit-Entry Adminstraction Bureau and other documents the local Exit-Entry Adminstraction Bureau requires. The bureau has the right to decide whether you can get the extension or not.

There is no limitation on the time to be out and then re-enter. You can just stay in other countries for several hours or longer.