The sun is almost directly overhead, the water is knee deep. In their family's flooded rice paddy, Mawin Chowhuaymok and his two brothers are stooped over a task that can easily be called the foundation on which Asian civilization rests.

They have left their shoes on a dike. Hefting an armload of 20-day-old rice seedlings, each man wades cautiously backward, at each step pushing a seedling's roots into the slippery paddy floor. The plants are spaced about 10 inches apart, just far enough to assure the roots won't choke each other as they grow.

The work looks exhausting, but Mawin, 24, claims it is not. He has planted since childhood and disposes of 50 seedlings per minute with ease. "When a lot of people work together, it can actually be fun," he says without breaking his rhythm.

The bright green seedlings now resemble spring onions. At maturity in October, they will be golden brown, each standing waist-high and bearing as many as 1,500 grains of rice. The 2.8 acres Mawin's family cultivates will yield more than three tons of rice.

About three quarter's of Thailand's people live in rural communities like Mawin's and most grow rice as their principal crop. Altogether they will harvest about 17 million tons of the grain this year.

Of all the questions village people ask Americans, the most common seems to be: "Is it really true that you don't eat rice?"

In East Asia a meal without rice is not a meal. The grain is food itself, the difference between prosperity and want. Its needs in the field dictate when people work and when they play. It is courted with countless religious rituals.

In Thai, as in many Asian languages, "to eat" translates literally as "to eat rice." When a Thai talks of cooking, he is actually talking of "making things that go with rice." He can refer to his possessions as his "rice and things."

Many historians credit the rise of East Asia's great civilizations to the refinement of rice agriculture. The Khmer Empire, for instance, built a complex grid of irrigation canals that allowed three crops of rice per year in places -- thereby freeing people to build temples, debate religion and embark on wars of conquest.

Often wars were directed at capturing neighboring states' most valuable assets -- their rice fields and the peasants who tilled them.In old Thailand, fields were often doled out to feudal noblemen whose rank could be determined by how much acreage they controlled.

Botanists classify the simple plant responsible for all of this as a grass. It exists in thousands of varieties. It is grown on the equator in Sumatra or as far north as Hokkaido Island in Japan, roughly the same latitude as New England. It thrives at sea level in flooded paddies or on dry hillsides at 5,000 feet.

In Thailand, the main planting season falls in early summer when the first monsoon rains soften and then flood the country's paddy land.

The farmer's choice of seed depends on how much water enters the field and on labor. If the farmer cannot control flooding depths or has only a few helpers, he usually plants "broadcast" rice -- so called because it is sown by casting handfulls of seed directly onto the soil. It can survive varying water depths and needs relatively little tending.

The Chowhuaymok family, however, has diked paddies where flooding can be regulated. It also has the requisite labor -- Mawin and his brothers -- to raise the more bountiful transplanted varieties of rice.

The seeds are first planted in a carefully tended nursery. These plots' dazzling green hue make them among the most pleasing sights in the Thai countryside.After three weeks the seedlings are meticulously moved by hand to the main paddies.

Transplanting must take place within a very tight time frame. Thus villagers often start their nurseries in sequence, then work cooperatively on each other's fields when the seedlings are ready to be moved. "We help them, they help us," say Mawin. It is one of the few examples of communal labor in the Thai village.

During its first month in the new paddy, the rice needs close tending. Mawin and his brothers will clear away weeds, hunt down rodents and birds and apply insecticide and fertilizer. After that, it is smooth sailing, until harvest in October.

Again, the villagers work in each other's fields, with much good-natured banter during the day and drinking and festivities at night. As the last rice is packed into the family bins or sold to visiting merchants, the cycle is completed for the year, though in some villages a second crop is planted.

The harvested rice appears on Thai plates in endless forms. There is the boiled rice Americans know. It also comes as a soup -- a favorite for late-night eating in Thailand -- snacks made from sun-dried grains, sweets made with coconut juice.

It is soaked and boiled until it becomes noodles. It is fermented into rice wines, which villagers must keep secret from the police.

By-products are used too: Husks go to feed pigs or insulate ice blocks being transported in barges. The stalk is left standing in the field, then burned away to fertilize the soil for the next crop.

Rice's role as the staff of life is guarded by religious ceremonies.Each spring Thailand's King Bhumibol Adulyadej plows a ceremonial furrow in Bangkok, using two specially blessed oxen.It is a centuries-old Brahmin rite to symbolically guarantee the fertility of the country's fields.

Villages in northeastern Thailand stage wild festivals which send 20-foot, homemade rockets into the clear blue skies of the late dry season. With much drinking and merrymaking on the ground, the heavens are symbolically fertilized by the rockets to make them pregnant with rain.

Transplanting and harvesting often begin with special offerings of food and incense to Mae Phosop, the supernatural Rice Mother. Every villager knows her: she becomes pregnant when the rice flowers bloom and her offspring, the grain, nurture humankind in the same way that a mother's milk, white and pure, nurtures a baby.

The rice she provides has a soul of its own, and the farmer must be careful to safeguard it. Through he or she may sell most of the crop to a merchant, a handful of grain is often carefully returned to the farmer to impregnate the next crop.

Anthropologists have recorded all manner of explanations of rice's place in the cosmic order. Some farmers use today's rice-eating habits as a barometer of morality. In previous epochs, it is said, when the human race was pure, people ate rice by itself with perfect satisfaction. But today vice is on the rise and simple rice is no longer enough. People must use sauces and curries to enhance its flavor.

Some Thais hold that the human body itself is composed of rice and eating the grain renews the tissues directly. It is the rice diet that distinguishes humankind from the other creatures on earth, in this view.

Farm machines and modern fertilizers have increased yields in Thai paddy fields. But they have not changed the basic cycle of life. Thus, at patriotic moments, Thais still like to quote a stone inscription dated 1292 found at Sukhothai, the capital of the first important Thai state:

"This Sukhothai is good. In the water there are fish. In the fields there is rice."