Getting a Chinese Tourist Visa in Thailand.

Hello my name is Wossen, I am Ethiopian currently living in PRC. I have been working in here for two and half years under Z type. And now that my contract is finished. I decided to tour PRC, but the government is telling me that I need to re enter in order to get a L type! I am just wondering if I can apply for a Chinese L type in South Korea. I have a few weeks left on my stay here . So an assistance would help a great deal. Also do i need an invitation letter to apply for the L type?