"Ya'll have high-speed Internet?" the recently returned refugee asked, getting only blank looks in response. "Oh man," he said, "my country needs a lot of work."

With peace in place after a 21-year civil war and the discovery of oil in the region, southern Sudan, one of the poorest places in Africa, suddenly has the potential to become one of the richest. It is luring home people such as Thian and galvanizing veterans of its long guerrilla war. As a new society emerges, roads and schools are being built, and the Internet is not far behind.

Thian left Sudan nine years ago, fleeing across the border to Ethiopia and eventually reaching the United States. There, he finished school and worked as a baggage manager at a Tennessee airport, saving money and hoping to return home.

He made it back this summer, but when he arrived, Thian found a devastated region where land mines blocked him from returning to his childhood village, 200 miles from this regional capital.

Even in Rumbek, desperate people tugged on his trendy clothes, begging for food. The depressing scene seemed far from the optimistic stories of peace he had read in the United States. With a bachelor's degree in aerospace administration from Middle Tennessee State University, Thian was offered a job instantly -- but he found it just as disorienting as his return.

"They asked me to be air traffic controller!" he bellowed, sweating under the pounding sun. "I was like, 'Dang, I don't really know how to do that.' But they will train me, so I was like, 'Okay, whatever.' "

Thian's willingness to take a chance embodies the general mood in postwar southern Sudan, where the stakes for millions of people are as high as their hopes.

More than 2,000 Sudanese professionals have returned from East Africa and the West since the north-south peace accord was signed in January. They include businessmen, college professors and basketball players, as well as recent graduates hoping to land a job. Some have reunited with family members; others, like Thian, have moved into tent-hotels set up by an American firm.

"We're not talking about reconstruction. We are talking about total construction. The U.N. has never undertaken anything like this," said David Gressly, the head of U.N. operations in southern Sudan. "The opportunities here are tremendous. But so are some of the risks."

On July 31, just weeks after Thian returned, John Garang, the leader of the southern rebel movement and key architect of the peace deal, died in a helicopter crash, causing concern that the shaky agreement would collapse.

Thian said he prayed when he heard the news and then unwound in his tent, spinning hip-hop songs on his CD player. But rioting soon broke out in the capital, Khartoum, and in the southern city of Juba, pitting Muslim northerners against Christian and animist southerners.

Violence has since subsided, and Salva Kiir Mayardit, Garang's longtime deputy in the rebel Sudan People's Liberation Army, has taken his place as the nation's vice president.

Even so, some harried returnees, including Thian, have made contingency plans to go back to the United States. But for now, he said, "I will stay and see how it plays out."

Thian and his friends from the diaspora often stroll the rutted, red-dirt paths around Rumbek. They have learned a local joke about riding home on "Bus 11." To explain, Thian slapped each of his long legs.

"One plus one equals 11," he said with a rueful laugh. "My legs are the only transport in South Sudan."

There are, in fact, no buses in Rumbek, the south's interim capital. Nor is there a bonded banking system, a newspaper, a civil administration or even a motorbike service to carry villagers to and from town.

Still, Rumbek is flourishing compared with places less than 100 miles away. In rural Aweil County, feeding centers are filled with malnourished children at rates even higher than in Niger, according to James Lorenz, a spokesman for Doctors Without Borders here.

The food crisis has been caused by a combination of factors, Lorenz said, including wartime land mines that impede farming, a surge of about 78,000 returnees from Khartoum, and several thousand refugees from Sudan's separate war in the western region of Darfur.

The region's land is so fertile that, once developed, it could feed the entire Middle East, a recent U.N. study found. But the war, which took 2 million lives and displaced 4 million people, has kept southern Sudan in a primitive state, with antiquated farm tools, no running water and women more likely to die in childbirth than finish primary school.

To build a modern society and retain public support, leaders must make the transition from guerrilla movement to government, unite fractious militia groups and quickly develop services and infrastructure.

Most people here see the discovery of oil as the best chance for prosperity. But they also fear it could bring nepotism, corruption and chaotic fighting, as has happened in neighboring Congo, where thuggish militias battle for control over gold and diamond resources.

"The enormity of the task is numbing," said Steven Weindu, the former rebel group's representative in Washington, who was visiting Rumbek. "We have a lot of sharp edges to smooth out. Anyone who returns has to have faith."

Sipping mango juice and smoking cigarettes, a group of Thian's friends crowded into an office set up to interview professionals for jobs.

"You name it, this place needs it. We have teachers with third-grade educations teaching fourth graders," said Peter Jola, who returned from Canada. In his adopted country he owned a garage. Now he's in charge of all government vehicles.

"The good thing is that opportunities are here," Jola said. "We can leapfrog and go straight to the best. We can forget landlines and just build a cell phone network. . . . Then again, I don't want to be too naive."

Already there is tension between the returnees and the local war veterans, some crippled, who feel the government owes them the jobs and training rather than the carpet-bagging businessmen back from Congo, Kenya and the United States.

"There has to be a balance between those with technical skills and those who fought in the bush," said Acuil Banggol, who played professional basketball in Egypt and has come back to earn money importing beer and digging wells. "I think there has to be enough work here to absorb everyone."

Banggol and Thian have formed a business association to enable returnees to meet residents and swap job tips. Thian said he was upbeat, even though his stomach was still adjusting to the water and he missed having high-speed Internet.

After working at the Rumbek airport this summer when it was under U.N. control, he said, he has now been assured of a good job there by the local authorities.