No, ASEAN member states would not be better off alone, because ASEAN serves a valid purpose and has a positive function. ASEAN helps its member states celebrate their culture. ASEAN helps those member states address economic issues and disagreements between nations. There is really no downside for these nations to be a part of this organization.
No, ASEAN member states would not be better off alone, because the Association gives them the opportunity to promote their collective interests as a region, while looking for ways to avoid conflict. Because economic development in the region continues as the nations struggle to emerge as modern, collaboration among nations can speed development. Membership is not costly and stands to improve life for citizens of these nations.