What kind of documents are needed in order for me to get a L two month visa?

A single entry L type is usually 30 days. So you either apply for a double entry L type or extend your single entry L after you come to PRC. You can try to apply from the Chinese embasy in Cambodia. But I am not sure if you can get it for sure. According to the latest regulation, applicants in the third country must provide their legal resident permits for employment or stuy etc there.

The required documents are the same. Round trip air tickets and hotel booking in PRC, your passport, filled application form and a recent passport size photo are required.