By TIMOTHY LELAND and

JULIE HATFIELD-LELAND

BON NON WAT, THAILAND: The man was lying on his back, his legs slightly apart, arms resting at his side, teeth glistening as though they had just been freshly bleached by a dentist.

They were good strong, straight teeth, but they hadn't been used to chew food for a long time. He had been dead for over 3,500 years.

We were standing in the middle of a graveyard. In fact, we were standing in the middle of several graveyards, stacked like a giant layer cake one on top of the other, each layer representing the passage of hundreds, in some cases thousands, of years.

Forget Six Feet Under; we were eight feet under and heading for twelve. Talk about culture shock. In a matter of hours, a Boeing 777 had jet-warped us back to a time on earth long before the birth of Christ. Two days after leaving Boston, we were exhuming the bones of men, women and children who had been laid to rest almost five millennium ago.

Graveyards don't figure in the travel plans of most tourists, but we had decided our first trip to southeast Asia would involve more than museums and bus tours. We wanted to experience the nitty-gritty of Thailand -- and working on our hands and knees below ground here in Bon Non Wat, a sparsely inhabited village northeast of Bangkok, we did just that In the truest sense, we were "down and dirty" in Thailand.

Along with nine other volunteers from around the world, we were taking part in an archeological expedition sponsored by Earthwatch Institute, searching for answers to the origins of the fabulous Angkor civilization.

The research under way here can be traced back to the late 1940's, when arial reconnaissance of the area near the Cambodian border revealed a strange phenomenon below: many of the tiny hamlets that dotted the countryside appeared to be located in the middle of faint but unmistakable circular depressions.

Closer inspection revealed that these hamlets were built on low mounds surrounded by a system of shallow moats, apparently scooped from the earth thousands of years go.

Today these prehistoric moats have become Exhibit A in a revolutionary new theory about the beginnings of prehistoric civilization in southeast Asia.

Until recently, conventional wisdom of archeologists and anthropologists has held that the influence of advanced societies in India and China gradually spread south and east into what is now Thailand, Cambodia and Laos.

It was believed that Indian technology, especially, was responsible for construction of the fabulous religious temple in Cambodia known as Angkor Wat, the largest religious monument in the world. Built between 9 and 13 A.D., it represents one of mankind^(1)s most astonishing architectural achievements.

Archeologist Charles Higham of New Zealand's University of Otago, however, has a different view of the origins of Angkor. Considered the world's leading authority on prehistoric cultures in Southeast Asia, Higham disputes the common belief that the indigenous populations of the region were backward people awaiting the arrival of technological advances from foreign sources.

He believes that the man-made moats and canals around places such as Ban Non Wat reveal a sophisticated system of water control and land management built by the earliest Thai tribes without any outside help. These and other signs of social complexity - such as extensive rice cultivation, skill at iron and bronze smelting, the exchange of goods in trade abroad - convince Higham that Thais formed a sophisticated society long before Angkor Wat was built. Which is what he is attempting to prove here at Ban Non Wat.

Over the past four years, a team of archeologists, grad students, Earthwatch volunteers and Thai workers have been removing the soil, inch by inch, and peering into the prehistoric "time capsule" that lies below the surface to learn more about the earliest Thais.

Using shovels, hoes, trowels, metal soup ladles and delicate dental picks, they have been unearthing the skeletal remains and valued possessions of the people who lived in that area over a period spanning the Iron, Bronze and Neolithic Ages, thousands of years ago.

Our archeological dig is taking place in a rectangular pit 60 feet long by 35 feet wide, and every morning, before any work begins, there^(1)s one important piece of business to attend to: Thai workers go down and remove any cobras or other snakes that have slithered inside during the night in search of mice.

Minutes later, activity in the "square," takes on the hustle and bustle of an open-air factory. In one corner a group of Thai workers hoe away the soil to extend the pit down another four inches, the maximum allowed at any given time. Thai women above the pit, wearing beautifully colored scarves around their faces to keep out the dust, lower buckets on pulleys to haul out the loosened earth.

A grad student is on all fours in another corner, his face a few inches from the wrist bones of an emerging skeleton. Using a dental pick and paintbrush he carefully scrapes and brushes the last few grains of dirt from four shiny shell bangle bracelets that circle its arm.

Nearby, Professor Higham is also on his hands and knees, peering down at the reddish, partially exposed rim of a burial pot that gleams in the dark soil. "This is an early Iron Age design," he proclaims. "The skull of the body will be right about here." He draws a circle in the dust. "We'll almost certainly find more pots on either side."

Peter Petchey, an archeologist from New Zealand, arranges a string grid on top of an exhumed skeleton prior to making a meticulous scale drawing of the body on a large sheet of white graph paper for future reference.

Above the pit an archeologist looks through a surveyor's level and shouts out numbers to a colleague below, carefully measuring the current depth of the site. A few feet away an Earthwatch volunteer, sitting at a makeshift table, is sorting and washing hundreds of pieces of broken pottery that have been found with the human remains.

By mid-morning it is hot under the colored cloth that serves as a sun protector, but the site still pulsates with activity. Unfazed by the heat, the Thai women rush the waste earth from the pit to a spoils heap, where it is sifted for the last tiny particles of pottery, bone, metals or anything else of significance.

The deepening hole in the ground seems to us, laymen who have never worked on an archeological dig before, in many ways like a giant block of ice slowly melting from the top to reveal the treasures encased inside -- ceramic burial pots of all shapes and sizes, shell jewelry, glass beads, bronze bells, marble anklets, clay smelting crucibles, axe heads, bronze ornaments and, most spellbinding of all, the skeletons of men, women and children who walked the earth before the birth of Christ.

But the "melting," of course, is all man-made. Every day the 65-member team at Ban Non Wat scrapes, scratches, chips and brushes its way ever deeper into the ground, as exclamations of surprise float up from the pit with each new find.

Life in the rural hamlet around the dig goes on much the way it did hundreds if not thousands of years ago. Every morning we jump into the back of an open-sided truck for the 45-minute ride out to the site. We pass huge open stretches of rice fields burned black to prepare for plantings in the wet season. An occasional palm tree stands tall against the fields and herds of Brahmin cattle watch us pass with soulful eyes and long droopy ears. Water buffalo plod across streams after their herdsmen. Tiny villages of wood houses are still built on stilts to keep out snakes and moisture, as postholes in the soil of the dig indicate was ever so. The children who live in the houses frequently come to the side of the dirt roads and wave at us, smiling shyly as we pass.

Before long, the Earthwatch volunteers begin to understand why archeologists suffer more than the average number of back and neck aches, given their uncomfortable daily crouching positions over the treasures they pursue. Our group hired an entire family to give us the traditional deep-tissue Thai massage on blankets spread over the floors of our rooms.

A week after arrival, we were assigned a section of the pit that hadn't yielded any recent skeletal remains, and expectations were low as we took up our trowels and began to scrape. But shortly after 9 a.m. the circular rim of a pot suddenly appeared in the dry yellow dirt. Fifteen minutes later, another came to the surface. . . then anotherS(and another. By the mid-morning tea break a large cluster of burial pots - some with beautifully flared rims, others small and bulbous, all of them a mix of red and black - had emerged from the ground, virtually intact.

"I think you've hit a super burial," Professor Higham exclaimed, using a term describing a mortuary site involving a person of high status, whose body is often decked out in bangles from wrist to shoulder, surrounded by scores of ceramic vessels and perhaps a bronze tool.

The casual banter that normally takes place in the pit stopped. All eyes focused at our feet as the objects slowly, magically, took shape in the loosened soil. Now the large trowels were exchanged for spoon-sized scrapers and steel dental picks. Working on hands and knees, head to head, we scratched the dry earth with greater urgency but more care, and an hour later, as one of us brushed away a layer of dust around something hard, the unmistakable gleam of shiny mother-of-pearl appeared on the surface. It was a bracelet on the right arm of a skeleton. We had located the body.

To the expert eye, pelvic bone structure can determine gender and possible age of skeletal remains, and Prof Higham determined that this was a young man. He had apparently been a very important one. When laid to rest he was wearing 14 shell bangles on one arm and four on the other, and he had a total of 12 pots to mark his grave - eight at his head, four at his feet - plus a tiny bronze bell. The bangles, the pots, the bronze bell and the skeletal remains had lain underground for thousands of years while the history of mankind unfolded. Now, like travelors from ancient times, they were in the light of day again.

To archeologists, burial artifacts of this sort provide important scientific clues to earlier times. But for us, the feelings were more personal than scientific, the questions more intimate, watching as the ancient soil fell from the bones of an individual who had lived and died long before the Roman Empire. What did this man look like when he was alive? Did he have a sense of humor? Was he good to his children? Did he tell jokes? Did he have a lot of friends? Was he happy? Was he afraid of dying?

And what of the people who placed him in the grave, who dug the hole and gently placed his body inside, then arranged the beautiful burial gourds at his head and feet? Who was there - his wife? His oldest son? Did they sprinkle water over the grave and then collapse in grief on the damp soil?

In many parts of the world one can dig for days and not find a single arrowhead or pottery shard. For anyone interested in archeology, however, or even just casually intrigued by the prospect of finding ancient artifacts in the ground, Thailand is the place to be these days.

"There's probably more undiscovered history here than in any other country in the world," says Nigel Chang, the project's co-principal investigator. "A tremendous amount of work remains to be done here. This region is practically untouched, archeologically speaking."

At our site, 261 complete skeletons had been exhumed in the month and a half before we arrived. When we left there were so many grave goods lying around that one had to be very careful not to trip over them.

Every day - almost every hour - something new is detected under the surface. "Hello, what's this?" the digger says, head down, peering closer to inspect the earth under the brush or trowel. A few minutes of diligent brushing gives the practiced eye a sense of what's underneath and the word goes out by some mysterious telepathy to everyone in the pit. Soon Higham ambles over, with the peculiar Woody Allen slouch of his, and renders his verdict.

On our final day, the verdict was stunning. "That, my friends, is almost certainly a Neolithic site" he said, looking down at the array of broken crockery one of us had uncovered and referring to a period stretching back more than 5,000 years ago. "See how thin the pieces are? And they^(1)re all broken up. That^(1)s very characteristic of Neolithic burials, when a dish was deliberately broken over the body at the burial. This is the period before recorded time, even before the Bronze Age. This is rare as hen's teeth."