Tourist Visa from foreign country

Hello, I am a South African working in South Korea. I will be completing my contract in Korea at the end of February 2013 and would like to travel to China and then go to Vietnam from there.
My visa for Korea will expire at the beginning of March, but I will not be re-entering there. Will I be able to get one for China if I have a ticket that flies from Korea to China to Vietnam? Are there any additional documents that I should add to the application?

Thank you