The Khmer currency in Funan period has not been defined the exact date yet. From some of researches, we we know that the ancient Khmer coins can be divided into two different eras: first era started from 1st century to 4th century and second era from 4th century to 7th century.

The government controlled all official foreign trade. In July 1979, the Ministry of Local and Foreign Trade set up the Kampuchean Export and Import Corporation (KAMPEXIM, the state trading agency) to handle exports, imports, and foreign aid. In addition, the National Trade Commission was created to be in charge of both internal and external economic coordination. In March 1980, the Foreign Trade Bank was formed to deal with international payments, to expand trade, to provide international loans, and to control foreign exchange. There were reports of special clearing arrangements for trade among the Indochinese countries and with some members of the Council for Mutual Economic Assistance (CMEA, CEMA, or Comecon--see Glossary).

Cambodia's major trading partners in the 1980s were Vietnam, the Soviet Union, and the countries of Eastern Europe, particularly the German Democratic Republic (East Germany), Czechoslovakia, Poland, Hungary, and Bulgaria. Cambodia also claimed to have trade relations with Japan, one of several countries that had recognized Sihanouk's Coalition Government of Democratic Kampuchea (CGDK) and had imposed a trade embargo on the Phnom Penh government of the People's Republic of Kampuchea (PRK).

Vietnam
In February 1979, Cambodia signed a Treaty of Peace, Friendship and Cooperation with Vietnam that formally strengthened "solidarity and cooperation" between the two countries. As part of the Vietnamese aid program to Cambodia, a joint scheme of pairing Cambodian provinces with Vietnamese "sister provinces" was inaugurated in the same year for the purposes of economic cooperation and of technical, educational and cultural exchange. Cambodia's Rotanokiri Province, however, was linked with two neighboring Vietnamese provinces--Nghia Binh and Gia Lai-Cong Tum. In addition, the municipality of Phnom Penh was paired with two Vietnamese cities--Ho Chi Minh City and Hanoi. Except for the municipalities of Hanoi and Haiphong, all of the Vietnamese participants in the scheme were located in former South Vietnam near their Cambodian counterparts.