Hello! I'm Ukrainian citizen. I changing my job now and need to renew working permit

and get new visa. In the middle of the process I need to fly back to Ukraine for 3 weeks. Ill get M type and after come back to China will get work permit.
The question is do I need to apply for new visa in Ukraine again ? As I know this visa give the right to stay in China during 30 days and only one entrance, but what about to come back?