What theories of International Relations can explain the conflict between China and some Southeast Asian countries about the Eastern Sea?
There is a current conflict and tension between China and ASEAN members (Philippines, Vietnam, Brunei and Malaysia) when China, which is known for being the strongest and richest country in Asia region, claims uninhabited island, Spartly Islands and the whole South China Sea as part of China territory
All major theories of International Relations would claim to be able to explain this. Let us look briefly at realism, liberalism, and constructivism.
Realists would say that the conflict is caused by a desire for power. All countries in the area know that that Spratlys and surrounding area appear to have resources that are worth having. All want them as a way to increase their power and security.
Liberals/idealists would say that the conflict is the result of insufficient institutions, dialogue, and trust. They would say that having more organizations like ASEAN (preferably including China along with its competitors) would bring greater understanding. Until that happens, conflict is likely.
Constructivists would say the conflict is a result of how China and the other countries perceive themselves and one another. China believes that it is a major power and should be the hegemon in its region. The other countries see China as a potentially aggressive power that must be resisted. Their concepts of themselves and each other drive them to conflict.
It is very difficult to objectively choose between the theories of IR. Each can plausibly explain things like this conflict. Because relations between countries are carried out by human beings, it is very difficult for us to ever know for sure what motives underlie actions that are taken by various countries.