Camera-wielding Western tourists ambush a dawn procession of monks in this once tranquil royal capital. Chinese engineers erect huge dams and blow up rapids on one of the world's last great untamed rivers.

Bulldozers are churning up jungly hillsides to lay roads into tribal villages of what some call Asia's last frontier. It's the basin of the mighty Mekong River, a culturally diverse, environmentally rich but economically impoverished region that is poised for vast transformation.

On the planning boards for these borderlands between China and the bulk of Southeast Asia are extensive road networks, electric power grids, tourism infrastructure and dozens of other projects totaling about $100 billion.

But opinions vary starkly about how such 21st-century inputs -- together with China's heavy hand -- will affect the isolated rice-growing villages, fishing hamlets and little market towns still living by ancient modes and rhythms.

"The ideal scenario would obviously be a prosperous region -- a growth of some 6 percent-plus -- but more importantly a prosperous region with equitable growth and an equilibrium with the environment," said Rajat M. Nag, who heads the Mekong Department of the Asian Development Bank, a key player in the region.

Meeting with fellow Lahu tribesmen near the Thailand-Burma border, Japhet Jakui is highly skeptical. He decries blasting of Mekong rapids by the Chinese and the increasingly easy, rapid river transport that allows amphetamine traffickers to reach tribal children as young as 4.

"All Lahu people love this river, but they will be hurt and they won't be able to do anything about it," said Japhet, head of the Lahu National Development Organization, one of many nongovernmental groups worried that the voices of the region's inhabitants -- 60 million of them, many from ethnic minorities -- won't be heard.

David Hubble of the Bangkok-based Project for Ecological Recovery has similar concerns.

"It's all imposed from above -- by the Asian Development Bank, the Mekong River Commission, the governments, big business," he said. "I don't think the people in the Mekong Basin will have any say in what happens to them in the future."

Critics outline a formula for potential problems:

The basin countries include three communist regimes (China, Laos, Vietnam), a military dictatorship in Burma and an increasingly authoritarian government in Thailand. Those, and the sixth basin country, Cambodia, already get poor to abysmal marks on the environment, corruption, official transparency and local participation in decision-making.

It is difficult to see how such a grouping can bring about development that takes common people and the environment into serious account, the critics say.

A major concern is China, especially its exploitation of the Mekong, the 3,032-mile-long lifeblood of the region endowed with biodiversity comparable to that of the Amazon.

The world's 12th-longest river springs out of the Tibetan highlands to flow through China's Yunnan province and on past the homelands of dozens of Southeast Asian tribal groups and historic cities such as Luang Prabang before emptying into the South China Sea in Vietnam.

Without consulting downstream nations, the Chinese built two dams and are putting up or planning six others on their stretch of the river. They are also behind the continued blasting of rapids in Thailand and Laos to allow passage of larger craft. The Chinese also plan as many as 13 dams on another major basin river, the Salween, and are engaged in extensive logging of Burma's great northern forests.

In Thailand, villagers along the Mekong say clearing of the rapids will destroy valuable fishing grounds. The Southeast Asia River International Network, a Thai environmental group, recently blamed the Mekong's unusually low water levels and abnormal fluctuations on the Chinese dams, although scientific data are still sparse.

Privately, officials in several basin countries express alarm at China's actions. But public criticism of the northern giant, with its increasing economic and political clout, is muted.

"We have realized that China will build dams if it feels they are necessary, but we hope to have dialogue on the impacts and technical issues," said Wolfgang Schiefer, chief of program coordination at the Mekong River Commission, a regulatory body China refuses to join.

Indeed, no single authority exists in the basin to resolve problems among the countries or to coordinate the welter of development programs descending on the region after decades of isolation by wars and geographic remoteness.

Among the variety of organizations and blueprints are the Asian Development Bank's Greater Mekong Sub-Region, the ASEAN-Mekong Basin Development Cooperation, the Golden Quadrangle forum, the Forum for Comprehensive Development, the Mekong River Commission and a number of U.N. agencies and international banks.

Nag, the Asian Development Bank official, said the needs are so great -- the region's per capita incomes average $200 to $400 a year -- that many participants are required and that decisions are made on a consensus basis with the bank serving as the "honest broker."

But he and Schiefer, at the river commission, acknowledge that coordination can be a problem.

"I think there is a commitment to avoid the chaotic and anarchic development of the past. But planning is always easier than reality," Schiefer said. "There will be aspects that cannot be controlled or will only be seen in hindsight. There are bound to be negative aspects of an economic opening-up."

Schiefer also agrees that there is some validity in criticism that development tends to take a "top to bottom approach."

"But we're trying to involve stakeholders in all programs. In some countries NGOs are not strong, but the commission is trying to point out their value to governments and we see a slow, but growing, willingness to accept them," he said.

Witoon Permpongsacharoen, who heads the Project for Ecological Recovery, says development plans for the Mekong Basin are using an old-fashioned model that focuses on resource exploitation.

"They have a vision of power grids and road networks and flow of goods. They see a road as an avenue for more goods to be shipped," Witoon said. "They don't consider the children and women and drugs that will be trafficked down that road. They are not considering the social, never mind the environmental aspects, of what they are doing.

"The Mekong Basin is unique in the world, an agrarian society of great diversity and environmental richness that will go the way of the industrialized world if developers have their way," he added. "Why can't it find its own way to development that would keep its unique character?"

Buddhist monks walk past a new restaurant sign in Luanprabang, Laos, in the Mekong River basin. Opinions vary about how development plans will affect isolated villages and fishing hamlets. Cheap goods from China, made available by rapid river transport, are offered for sale in the town of Mae Sai, Thailand, on the border with Burma. A girl from the Lao Huay tribe runs through the village Luang Nam Tha. Once considered hidden, places in Laos and other Southeast Asian nations are being squeezed by corruption and development.