By the time Chris and I started down the southeast bend of the river above Thakaek, the Mik Sip had traveled more miles down the Mekong than most Lao citizens travel in their lifetimes. As we steered our northern-style fishing vessel into the southern reaches of the river, we may as well have been driving a dogsled into downtown Dallas. Fishermen in small, long-tail powered dugout canoes stared in confusion or bemusement as Chris and I thumped past in a high-gunneled, canary-yellow craft that was twice as long and half as maneuverable as anything else on the river.

Since the logistics of a two-man crew pretty much precluded socializing, Chris and I drove straight through to Thakaek. Piloting in shifts, we stuck close to the tobacco fields of the Lao shoreline as the river gradually widened. By late day, we could no longer make out the fishing boats on the Thai side of the Mekong.

When the sun went down amid an orange halo of burn-off smoke from the Thai fields, we drove the last two hours to Thakaek by moonlight. In the dim neon glow, the shores of the Mekong dissolved into a bluish veil of noises. The rattle of the Mik Sip's engine reverberated from the Lao bank with a warping echo, sounding like some back-masked message from Babel; dim strains of karaoke drifted across the waters from the Thai shore, as eerie and tuneless as white noise. Whenever Chris shouted to me from the pilot's seat, it sounded like there were 100 of him in a very large and empty room. Though we certainly weren't on the river much past 8 p.m., it felt like time had stopped altogether. We pulled into Thakaek as enchanted and spooked as Huck and Jim below the Ohio.

I fell asleep in my hotel room within an hour of arriving, and woke up disoriented at 4:30 in the morning. Hoping to straighten my bearings, I went for a walk through the darkened pre-dawn streets of Thakaek.

If Luang Prabang is a tiny Manhattan, then Thakaek is a Laotian St. Louis -- an 1850s-style gateway city, where little girls try on their mother's lipstick by kerosene lamp light behind the shuttered windows of crumbling mint-green Lao-French homes, and blue banners advertising Pepsodent flutter above dusty piles of red brick in the old colonial town square, and sad chickens screech like broken radios in the moments before sunrise.

As I walked, Nakhon Phanom, Thailand, blazed in electric splendor just across the river -- a vision of an alternative future -- its riverbanks hemmed with smart concrete walkways, its avenues webbed over with telephone lines, its temples as clean and uniform as McDonald's franchises.

In a century defined by technological progress and Western standards of living, the Lao shores of the Mekong often feel like a dusty asterisk in the history books. Indeed, some 85 percent of Laotians still survive on a subsistence lifestyle -- farming or fishing for food, building their homes from native materials and occasionally bartering for consumer items.

Outside influences look to change all that. Just a few decades after having dropped 2 million tons of bombs on Laos (as part of an ill-defined "secret war" that reduced the peasant culture of Xieng Khouang province to rubble), the United States has already poured $1.5 billion of investment into Laotian modernization and economic-development schemes.

The city of Thakaek, though, symbolizes the potential of a much stronger influence on Lao society: Thailand. In 1996, Bangkok and Vientiane signed a memorandum of understanding to build a bridge connecting Thakakek with Nakhon Phanom. Thus -- with the increased flood of Thai commerce bound to arrive on the Lao shore -- Thakaek represents how Laos is at a sensitive crossroads: primed for changes that will likely redefine the country in another 20 years.

It has been suggested, of course, that this is a bad thing -- that avoiding foreign influences and maintaining the purity of local culture is somehow more ideal. But a close look at Lao culture itself shows how it's too late to arbitrarily stop time and make judgments of cultural purity. After all, the basic precepts of Lao mythology, philosophy and religion are heavily influenced by the ancient Khmers (who themselves were influenced culturally by India), most Lao pop culture is already Thai-derived and for hundreds of years there was no distinct border between Laos and Vietnam.

All of this in addition to the fact that -- even in the charming pre-dawn streets of Thakaek -- I never once saw any Lao citizens who could knap flint in the manner of their Stone Age ancestors.

Within two hours of my morning walk, I was back on the river. While I'd been asleep the night before, Chris had invited Liz and Duncan, a good-natured young English couple, to join us for the final stretch.

The four of us made it two days downriver from Thakaek -- and not more than an hour past Savannakhet -- when I personally drove the Mik Sip over a submerged rock shoal, snapped the propeller off and set us adrift in the swift current.

"Well," Chris said with a trademark phlegmatic drawl that indicated he was panicking, "if we don't start paddling right now, we're gonna lose this boat."

Thus began our descent of the Khemmarat rapids.

If any English-language travel guidebooks offer the slightest shred of specific advice on navigating difficult sections of the Mekong, I am not aware of their existence.

Going into the Khemmarat rapids, the best description of our watery obstacle came from Marte Bassenne's 1909 travelogue -- which vaguely placed the rapids somewhere between Savannakhet and Pakse, and grimly noted that this stretch of the Mekong River "is like a common grave of unlucky victims, because one seldom finds a corpse." Francis Garnier, whose expedition team portaged around the rapids in 1866, wrote of Khemmarat: "Nothing can express the horror of this spot, where the yellow waters twist over and through the long narrow pass, breaking against the rock with a fearful noise."

Chris and I had disregarded the hyperbole of our French predecessors for three reasons. First, we were in the middle of dry season, so the rapids would not be as fierce as Garnier and Bassenne had witnessed. Second, we had purchased a sheaf of detailed topographical maps of the area from the national geographic service in Vientiane. Third, we figured that the ubiquitous Lao fishermen -- who had been quite helpful in pantomiming instruction thus far -- would warn us if we were about to motor into certain death.

After I broke the propeller on the shoal below Savannakhet, we were able to paddle to a broken concrete pylon away from the current and save the boat. During the French colonial era, that pylon might have warned me off the rocks in the first place. Unfortunately for us, the Savannakhet to Pakse portion of the river isn't used for long-haul commerce anymore, and the century-old pylons have been worn down to amorphous lumps of cement and cobbles. For our purposes, the pylon did little more than provide me with something to steady the boat on as Chris plunged under the stern to install a new propeller.

Once the Mik Sip was up and running, we headed downstream for what would become 36 continuous hours of melodramatics. Low water had indeed provided us with a weaker current -- but it had also split the river into a foaming braid of channels splayed out amid a maze of rocks. When we weren't churning through the whitewater, it seemed, we were getting stuck on a shoal.

Chris drawled nervously at us the whole time, and continuously improvised methods of staving off disaster. When the channel narrowed to a boil, Chris put Liz in the bow and had her signal upcoming dangers. When waves from the rapids began to wash over the gunwales, he had me squat over the engine with a plastic mat so we wouldn't stall out in the middle of the whitewater.

Around sundown the first day, we eddied-out near a huge riverside sand dune that made for a perfect campsite. After collecting my share of the night's firewood, I went down to the water's edge to watch the first stars come out. Something about the day's dangers had sharpened my senses; I listened to the languorous murmur of the river with an acute feeling of joy. As I breathed in, I imagined the tiny bits of oxygen attaching to the wet walls of my lungs and sifting off into my bloodstream.

Just after noon the following day, we came upon the most daunting rapid we'd seen yet: a fat tongue of water that spilled out in a fury between two huge black rocks. Intimidated, we stopped for lunch.

Positioning himself high on the bank above the rapid, Chris peeled a hard-boiled egg and stared out at the foaming water with an edgy silence. When he'd finished eating, he came down from his perch. "To hell with it," he said.

Five minutes later, he took us straight down the middle of the tongue, and that was the end of the Khemmarat rapids.

- - - - - - - - - - - -

Years ago, Lao myth tells us, men and gods used to meet. As generally happens in such situations, the humans blew that arrangement by being foolish and arrogant.

When mankind insolently refused to seek a livelihood beyond hunting and fishing, the gods flooded the world. Three chieftains managed to escape the flood by building a floating house. When the waters receded, the gods gave the chieftains a buffalo, so they could plow the earth, plant crops and live in a civilized manner. When the buffalo died, three gourds grew from its nose -- and when the chieftains cut open the gourds, humans poured out to populate the world.

Below the rapids of Khemmarat, where the Mekong gradually twists its way down into an isolated, sun-baked canyon, one is tempted to take this myth at face value. The only inhabitants of this limestone gorge -- which is fluted with ledges and fringed at the top with virgin forest -- were gypsy fishermen, who seem to have secretly dodged the mythic flood and held on to their uncivilized ways. Living directly on the canyon cliffs in thatch huts, and climbing from ledge to ledge on an elaborate system of wooden ladders, the river gypsies looked otherworldly -- larger than life -- like they were impassively waiting for Jesus to come back and make them fishers of men.

We camped that night on a narrow dune that hadn't seen footprints in ages. I entertained myself for the good part of an hour just walking the contours of the sand, turning every so often to watch the tiny avalanches set off by my presence. When I awoke in the bow of the Mik Sip the following morning, the sand next to the boat was laced with the tracks of voyeuristic rodents.

South of the canyon, the Mekong swelled to a width of over a mile and doglegged away from Thailand. On this clean blue stretch of river, the waters were once again awash with passenger ferries and huahoua-leim freighters, plying the stretch between Pakse and the Thai border.

By the time we'd arrived in Pakse to order an enormous restaurant dinner and toast our survival, Chris was already overstaying his visa. He departed for Thailand the next day, leaving me the sole owner and most experienced operator of the Mik Sip.

In a way, my Mekong adventure ended with the passage through the rapids and the canyon.

This is not to say that the river becomes any less interesting, beautiful or even challenging below Pakse -- it just means that after Pakse I assumed the helm of the Mik Sip, and I wasn't able to pay attention to much beyond the course of the river and the boat itself.

Like Twain had in his river piloting days, I had lost the river by learning the river: I had traded aesthetics for science. But for me -- as for Twain -- the challenge of driving the riverboat was reward enough for all the lost splendor.

As we made our way downriver, Liz and Duncan would point out the big white-and-brown birds of prey soaring above, the abandoned fishing villages that sagged like shipwrecks on the sandbars or the finger-sized fish that jumped from the water and skittered along in our wake. We even stopped for several hours at the ruins of Wat Phou -- a haunting, half-collapsed sandstone temple where pre-Angkor Khmer statues lie headless, half-buried and stained with Pepsi and one's sense of being amid "time-worn dreams of adolescent reverie" (as Garnier put it) is offset by the trash-strewn, weed-tangled feeling of touring a recently abandoned drive-in movie theater.

For the most part, though, I was lost in a curiously satisfying world of pylons, channels and currents -- of bilge water and the correct fuel mixture for our 10-horsepower Briggs and Stratton.

Two days below Pakse -- 22 days after having first boarded the trusty yellow boat -- I drove the Mik Sip into Cambodian waters on the Lepou tributary of the Mekong.

Just above its Laotian terminus, the Mekong enters a new geophysical region -- splitting into dozens of channels and thousands of small islands. Appropriately, the Lao name for the area is Siphandone -- "4,000 Islands." Graced with freshwater dolphins, peaceful lagoons and majestic waterfalls (including Khong Phapheng, reputedly the world's widest waterfall), Siphandone has no rival as a landlocked tropical island paradise.

After our final day on the river, Liz and Duncan threw me a farewell dinner on Khong island, the largest and most accessible of the 4,000 islands. After dinner, we went to the community basketball court, where a raucous pop concert was already under way.

Onstage, a group of teenage girls performed a sequence of bump-and-grind dance moves to the rhythms of the music. Dressed in frumpy orange dresses and wearing socks under their sandals, the girls looked strangely dated, like something I might find in the pages of my mom's 1961 Westphalia, Kan., high school yearbook.

The Lao pop music itself (which is perhaps still recovering from a short-lived 1976 Communist edict banning rock music, cosmetics and animal sacrifices) was awful beyond metaphors.

- - - - - - - - - - - -

The following morning, I rose early to take the pre-dawn ferry to the mainland, where -- in deference to my expired visa -- I would catch a series of buses to the Thai border. Joining me at the first bus stop was one of the orange-dress dancing girls from the night before. Standing there in her subdued street clothes -- sleepy and wistful -- she looked like a morning-after Cinderella.

Which is what I felt like, after three weeks of clean sand, campfires and silent sunrises on the shores of the Mekong.