Cambodia is located in the southern part of the Indochina peninsula in Southeast Asia and spans 69,898 square miles in area. It is bordered by Laos, Vietnam, Thailand, and the Gulf of Thailand. Cambodia has a population of more than 15 million people. Roughly 95% of that population practices the official religion of Theravada Buddhism. Phnom Penh is the largest city in Cambodia as well as its political, economic and cultural center. Cambodia is a kingdom consisting of an elective constitutional monarchy, with the monarch chosen by the Royal Council of the Throne as head of state. The Prime Minister serves as the head of government. Currently, the Prime Minister is Hun Sen, the longest-serving non-royal leader in Southeast Asia. Hun Sen has ruled Cambodia since 1985.