Khmer - The Qin Empire Speak

That is not historically accurate. The Qin Empire (221–206 BCE) spoke a form of early Chinese, specifically a variety of Old Chinese, which is part of the Sino-Tibetan language family. Khmer, the language of the Khmer Empire and modern Cambodia, belongs to the Austroasiatic language family and was spoken far to the south, in mainland Southeast Asia. No evidence connects the Qin dynasty to the Khmer language.