Laos is a landlocked country located in Southeast Asia bordered by Burma, Cambodia, China, Thailand, and Vietnam. Most of the country is mountainous and thickly forested, and the Mekong River forms a large part of the western boundary with Thailand. The government system is a Communist state; the chief of state is the president, and the head of government is the prime minister. Laos has a mixed economy in which the government has implemented gradual economic and business reforms to liberalize its domestic markets. Laos is a member of the Asia-Pacific Trade Agreement (APTA) and the Association of Southeast Asian Nations (ASEAN).