1. Not all ASEAN countries have SCS issue with China except PH, VN, Malaysia and Brunei.
2. Trade dependant with each other (especially with China) mean most of the countries play the game smart instead of direct confrontation.
3. At this stage, only PH and VN have issue with China. The other two countries just sit back and watch. Some countries try to pull other nations into the dispute to gain support but failed.
4. Whole ASEAN cant unite because of their differences. U got first, third world countries and failed states in the same region. Different religions, languages, cultures and internal security issue in various countries... good luck.