Is there a direct route from Yunnan to Tibet?

Of course there is. The Yunnan-Tibet Highway is the highway from Yunnan into Tibet. It is now also called the G214 National Highway. It runs from Jinghong in Yunnan to Xining in Qinghai, with a total length of 3,256 kilometers. In Yunnan, you enter Tibet from Diqing Tibetan Autonomous Prefecture.