Association of Southeast Asia Nations (ASEAN) is a treaty organization established in 1967. It currently has ten members. The original five were Indonesia, Malaysia, Philippines, Singapore, and Thailand with Brunei Darussalam, Cambodia, Laos, Myanmar (Burma), and Vietnam joining over the years. The goals of ASEAN are to foster regional economic growth and promote regional stability and development. As an advocate of the less developed nations of Southeast Asia, ASEAN has become a key player in the international trade negotiations. The ASEAN Free Trade Area was initiated in January 1992 with the intent of reducing comprehensive tariff reduction in the region.
The ASEAN webpage has a great deal more information about the structure, purposes and activities of the organization. It also provides information about the ASEAN Treaties.