In my opinion, China has two main priorities.
Number one, China must annex Southeast Asia for several reasons:
1. Agricultural land.
2. Fresh water.
3. A coastline on the Indian Ocean.
4. Control of the Strait of Malacca.
Keep in mind, I'm not talking about an invasion of Indonesia or any other island. I'm talking about the annexation of the areas of Southeast Asia that are land-connected to China. The PLA can take these areas easy.
Number two, China should annex Central Asia for the oil, natural gas, and uranium. Central Asia is landlocked. The PLA can't lose here.
Forget about democracy. Democracy means haggling and negotiations that may drag on for decades. Take these regions by force when the time is right.
Does China have the ability to wage a massive ground war across Asia? The answer is yes. China has built the largest auto industry in the history of the world producing over 22 million vehicles a year. This is a transportation system that can deliver tens of millions of troops and maintain supply lines across Asia.
2013 Statistics | OICA
Road and highway networks already extend across Asia.