The Religions of South Vietnam in Faith and Fact, US Navy, Bureau of Naval Personnel, Chaplains Division , at sacred-texts.com
Ancestor Worship--Worship of Nham-Dien
Among the gifts of the Chinese to Vietnam during 1,000 years of occupation, and as the big neighbor next door, is ancestor worship Ancestor Worship is more than just the worship of "spirits" of one's deceased relatives; it is also the veneration and worship of great men, or at least the "spirits" of these great men, and many temples have been erected in which that particular personage may be worshipped. Among the recognized religions and places of veneration or worship in Vietnam are many of these temples-some quite small and simple, others large and showy.
Since rice is the major foodstuff and the staff of life to the Vietnamese, with the average consumption computed to be a bit over two pounds a day per adult, anyone aiding rice production in a notable way would become a famous man. One such individual who lived about the time of Christ was Nham-Dien, governor of Thanh-Hoa, which today is a province in North Vietnam. As rice growing seemed not to produce sufficiently for the labor expended, the farmers turned to fishing and hunting (wild game such as elephants, tigers, deer, are still available in Vietnam), and the people suffered from insufficient diet.
Nham-Dien--who apparently had been either raised or educated in China--taught the Vietnamese the art of wet rice culture. So that water might be readily available, he laid out canals and divided the lands into small plots which could be flooded readily from the canals and rivers that are abundant in Vietnam.
Two thousand years after Nham-Dien introduced wet rice culture to the Vietnamese, his methods are still used. Throughout the length of South Vietnam, the rice fields, divided into small plots and watered by canals that never seem to dry, are constant reminders of this long-dead governor. To the Vietnamese, who study and learn much of their material by rote, Nham-Dien is still a vibrate personality whose spirit can help those who worship him. To aid such worship, there are a number of temples-especially in his province of Thanh-Hoa-built in his memory, Because of his work with rice production, and his rules regarding marriage, Nham-Dien is considered to be among the great men of his country.