The Religions of South Vietnam in Faith and Fact, US Navy, Bureau of Naval Personnel, Chaplains Division , at sacred-texts.com
Non-Christian ancestor worship begins at the time of death. As soon as death is a fact, the ethnic Vietnamese cover the corpse with a square piece of red cloth. Often a bit of cloth is made into the shape of a doll representing the body so that it might receive the spirit of the dead one. Then the corpse is washed, clothed in best garments, and placed on a bier in the casket. Mourning is announced with such details being spelled out by law. Usually a complicated ceremonial rite is used for burials. The grave is often dug according to geomancy.
From the day of death, there will be a lighted candle on the ancestor altar with attempts to keep a flame there constantly; in addition food is placed there for the spirit of the dead individual. Mourning for members of the immediate family supposedly lasts for three years with yearly ceremonies on the anniversary of their deaths. When a father dies, his daughter may not marry for three years due to mourning customs. Most Orientals regard the death anniversary more important than birth dates, for who knows at birth what an individual will achieve or become.
While there are differences of opinion, it seems that death among the ethnic Vietnamese is believed to be part of the return to eternity. A reincarnation in some form will be decided by the sum and value of the life of the deceased as well as by the prayers said to one's spirit. On death anniversary celebrations, the first day of the year, lunar festival holidays, and all important family events such as birth and marriage, worship at family ancestor altars is performed.
To the average family of ethnic Vietnamese the presence of the spirits of their ancestors is vivid and is as much a part of reality as are the living. No offense by word, deed or thought should be given; rather honor must be rendered so that one's own moral and social standing is improved. One authority has pointed out that to the Vietnamese "a country is composed as much of the dead who laid its foundations as the living who perpetuate it".
The ancestral veneration of Chinese culture is a link uniting the dead and the living members of the family. The social virtue of filial piety, as taught by Confucianism, is greatly esteemed and is a cohesive element in binding the family and clan into a unit. The living believe that such worship provides a channel of valuable services between the living and the dead-careful observations reveal how deeply filial piety affects the social, political and economic structures in South Vietnam and demonstrate the necessity of understanding people as human beings wherever found.