The Kingdom of Cambodia is a country in Southeast Asia that borders Thailand to the west and northwest, Laos to the north, Vietnam to the east, and the Gulf of Thailand to the south. The geography of Cambodia is dominated by the Mekong River (or "the great river") and the Tonlé Sap ("the fresh water lake").The kingdom is a constitutional monarchy with Norodom Sihamoni as king who has reigned since 2004. Phnom Penh is the kingdom's capital and largest city, and is the center of political, commercial, industrial and cultural activities. Siem Reap, a city located near the famous ruins of Angkor Wat is the gateway to the Angkor region, and is Cambodia's main point for tourism. Battambang, the largest city in western Cambodia, is known for its rice production, and Sihanoukville, a coastal city, is famous for sea port and beaches.