Simultaneously, they are trying to squeeze as much land as possible from their neighbors. Recently, Chinese soldiers killed 20 Indian soldiers who foiled their land-grabbing attempt.
The issue will be in areas wherein China can claim supremacy without much resistance, for example, off the coast of weaker neighbours in the region.
It's a pretty bold ploy - at the same time, I actually believe that the 'chip wars' will be more important!
I do agree that coastal waters of certain ASEAN countries, which are practically defenseless, are at a significantly higher risk.