Most of the people are Khmer, a racially diverse group that arrived in Southeast Asia in about 2000 BC. They speak Khmer, a language that is a member of the Mon-Khmer group of Austroasiatic languages spoken in northeast India and Indochina. Men and women both generally wear an upper jacket and a saronglike lower garment called a sampot.

Almost 4 million people lived in the Khmer Empire at its height from the 11th to the 13th century AD. Conquest by Thai forces in the 14th and 15th centuries reduced the population by about half. Wars during the 17th to the 19th century reduced the Khmer to about 1 million people by the mid-19th century. By 1960, however, the number of Khmer had again increased to almost 5 million, and by 1995 the number of Khmer had reached more than 8 million.

Aboriginal groups occupy the upland area around the borders of Cambodia. Muslim Chams live in villages in the eastern part of the country. For centuries colonies of southern Chinese have made their homes in Cambodian cities, and some have intermarried with the Khmer. Approximately one third of the Chinese live in Phnom Penh, the capital and largest city (see Phnom Penh). Vietnamese settlers began arriving in southeastern Cambodia in the late 17th century. Thai live along the western fringes of Cambodia, near the border with Thailand.

The Khmer are primarily an agricultural people. Most of the Chinese live in cities and work in nonagricultural occupations. Some of the ethnic Vietnamese of Cambodia are farmers or fishermen, and others are artisans or merchants in the cities. In the rural lowlands, the Khmer live in villages.

The Khmer have long been practitioners of Buddhism, though many rural people follow ancient folk religions. During the 14th century the Khmer shifted from the Mahayana to the Theravada, or Hinayana, tradition, of Buddhism (see Buddhism). Young Khmer men normally spend a period as priests associated with a temple.

A farmer operates a water wheel, which is used to bring water from a nearby stream to his fields. Rice, the most important crop in Cambodia, requires fields to be flooded with a few inches of water. Farmers plant about four-fifths of their cultivated land in rice.