The worship of Thông Thiên (Heaven-Communicating) is a widespread folk belief in venerating Heaven in the South of our country. According to folk beliefs, Heaven ranks above Buddha among the objects of worship, in the order “Heaven – Buddha – Saints – Gods.” Therefore, worshipping Heaven is the very first act of devotion for every individual and every household.

Before 1975, in most rural areas of the South, nearly every home had an outdoor Thông Thiên altar in front of the house (often called the Ông Thiên altar). The altar was usually simple, made of wood: a single post about 1.5 meters tall topped with a square wooden platform, each side around 0.4 meters. More affluent families built concrete posts and tiled them. On the altar there was always an incense burner and several small teacups filled with rainwater.

On important days such as the first and fifteenth of the lunar month, two bowls of rice and salt were added, along with plates of fruit. Every evening at dusk, the homeowner would light a single incense stick, clasp hands before the altar, and pray to Heaven for blessings, health, and peace… hoping the rising smoke would carry their sincere wishes up to Heaven (thông thiên – “communicating with Heaven”), so that Heaven might bless their family and loved ones.

The Thông Thiên altar serves as a spiritual bridge connecting humans with Heaven, with ancestors, and maintaining the link between Heaven and Earth, between the living and the departed. This is symbolized by the daily lighting of incense at dusk—the moment when day transitions into night—and the incense placed in the burner, which stands between Heaven (above) and Earth (below).

The worship of Heaven also appears in many religions present in the South. In Cao Đài, Heaven is worshipped as Thiên Nhãn (“Heavenly Eye”), represented by a single eye symbolizing the all-seeing, all-powerful Supreme Being who observes every human action. In Hòa Hảo Buddhism, besides venerating the Nine Ancestral Generations and national heroes, each devotee’s family maintains an outdoor Thông Thiên altar in front of the house to honor Heaven and Earth.

For farmers, Ông Trời (Mr. Heaven) is seen as a powerful, miraculous, and compassionate being who can save people in times of need. When facing misfortune, people “pray to Heaven and Buddha” to “ward off danger and calamity.” Heaven is sometimes personified and humanized, addressed as “Ông” (Mr./Grandfather),

Ông Trời has eyes:

“Oh Heaven, look down and see,
My wife beats me with a palm-leaf stem.” (folk verse)

and has ears:

“Hey, don’t take advantage of others.
Buddha has eyes, Mr. Heaven has ears.” (folk verse)

And Ông Trời bears responsibility: people believe “Heaven gives birth to the elephant, Heaven provides the grass,” “Heaven gives life, Heaven nurtures,” and “Heaven never forsakes the sincere heart.”

Thus, Ông Trời has moved from being a distant “supernatural being” into the daily life of Southern farmers—understanding their thoughts and feelings, witnessing their joys and sorrows, seeing their hardships, and ready to lend a helping hand. Ông Trời becomes as close as grandparents, parents, or family members. That is why worshipping Heaven feels completely natural and ordinary.

Southern people are straightforward and open-minded in life and customs, so religious syncretism is clearly evident. Many Thông Thiên altars also include worship of Ông Tà (the Earth Spirit) nearby—sometimes a few stones placed beside the incense burner, or a small corner at the base of the altar. On death anniversaries, festivals, or Tết, people often combine offerings to “Ông Trời” as well.

If there is a tray of food offered inside the house, the Thông Thiên altar outside also receives offerings—fruit, a plate of sticky rice, or sometimes wine and meat. On New Year’s Eve, every family places a five-fruit tray or a round, full watermelon on the Thông Thiên altar to pray for abundance throughout the coming year.

Today, many rural areas in the South still maintain this custom. Observing a Thông Thiên altar reveals the simplicity, sincerity, and genuine faith of the Southern people. Yet beneath this simplicity lies the ancient yin–yang philosophy that has existed for thousands of years among the Lạc Việt people, symbolized by the square (Earth – yin) and circle (Heaven – yang).

The square altar represents Earth (yin), while the round incense burner represents Heaven (yang). The Southern people’s constant yearning for harmony and perfection is quietly expressed every day through the Thông Thiên altar: square and round, yin and yang.

According to Cà Mau Online