I wasn't looking to get into movies, when I stopped by the office of John Gray's Sea Canoe a few months ago. I wasn't even looking to go sea canoeing. My intent was far more pedestrian — I was hoping for a few quotes regarding the ecology of Trang Province. But John said he doesn't go there anymore. Maybe I'd like to join a special media adventure to Tarutao Island instead? Two guys who work with Hollywood were coming to shoot his new promotional movie, but I was welcome to tag along. "We'll be exploring for five days and four nights," he said, running quickly through an itinerary of caves, mangrove forests and waterfalls both on the mainland and out on the island. I felt as though I'd just won a fellowship, or a Porsche, without having entered the competition. Of course I would go!

When my fiancée Yupin and I arrived at the office on the morning of our departure, we found not one, but two film crews: the Hollywood guys, who were actually based in Hawaii; and a man with a little dog — a Jack Russell terrier, one of those breeds that's gotten trendy in the States over the past few years. They're supposed to be smart.

Now, I'm ambivalent at best towards dogs, and Yupin's tolerance is less than mine, but this one was cute. He stood there near the coffee table, looking up with this big friendly smile, panting and exuding that dog enthusiasm that's always asking, "When are we going?" Tim Karsten was his human counterpart. This warm, peaceful fellow had lived a long time in Santa Fe, one of the new age capitals of the world; he was just finishing up some emails and telling us about his deal — "Travels With The Sparkster" — a show he was filming and pitching to various well-known children's television networks. He couldn't use Sparky's real name, he told us, because the US firefighters association has trademarked it for their Dalmatian. Sparky. Fire… Get it? Though one would think firefighters would prefer a less incendiary name for their mascot. Something like, "Come 'ere, Water! Good boy!"

Our journey would take us deep into southern Thailand, to Satun Province, on the border with Malaysia. On the drive, we discussed our backgrounds, futures and upcoming adventures, commented on the passing rubber and palm plantations, and spoke of psychic abilities and life's callings. But mostly we talked about Sparky — quite possibly the first Jack Russell Terrier to tour the Taj Majal. They had travelled throughout Europe, been held up by red tape — Sparky's visa — for weeks in Mozambique, watched pods of right whales from the southernmost point in Africa, and chased fireflies in Virginia.

Everywhere they go, Sparky tries to play with local kids, Tim's way of promoting world peace by teaching that we're all the same, all over the world. He sets up appointments with schools in all the countries they visit, and presents the show from Sparky's perspective. Even people who don't like dogs get warm fuzzies when the little guy pokes his head up. By the time we got to Satun, Yupin, the least dog-friendly of us all, had taken command of his leash.

Over the following days we were to follow John, the "Caveman," deep into the history of the earth, into chambers barely affected by passing millennia, through mangrove forests where pythons coiled in tree-crotches, and along bays and beaches where white-bellied sea eagles and brahminy kites dove and porpoises breached the surface. The natural wonders were breathtaking, awe inspiring — once-in-a-lifetime stuff. Yet, while we absorbed the world of Tarutao each in our own personal ways, most of our socializing centred on our smallest cohort, both the star of Tim's movie and the heart of our trip.

Sparky mostly played his part well. A born actor, he mugged for the camera, posing on the bows of canoes, demanding attention in crystalline caves with echoing barks that drew both the filmmakers' lights and cameras. At lunch, deep in a mangrove forest at low tide, he leapt from the boat into the black mud, rolling over and over, delighting as much in the cool moist earth as in our cheers and laughter. He emerged black as a tar baby, grinning from ear to ear in a self-satisfied smirk.

Occasionally he deviated from the storyboards. At the Ao Sane ranger station, he shacked up with a bizarrely met poodle and her brood, prompting a lot of good-natured ribbing from the fellows in the morning. I had grown to believe that the cliché about dogs chasing cats wasn't even really true. But the few times they appeared, Sparky transformed into white lighting, his tiny legs ferociously pumping as he ripped through the jungle while Tim scolded from the beach, "No cats! Sparky! No cats."

A moment of fear beset the group when we camped at a waterfall. There, in the parking lot, a jet-black scorpion brandished its claws and swung his poison-bulb tail. While we agreed that it probably wouldn't kill any of us, it could surely do a number on the little dog. A team broke off to keep Sparky away from the nasty bug, while the rest of us stood watching it in the glow of two or three cigarette lighters. Then, the next morning, deep in the blackness of Seven-Turn Cave, Sparky slipped from the bow of Tim's canoe into the moving water of the subterranean river. Tim, without a flashlight, somehow recovered him, and the Caveman roundly reprimanded his staff for neglecting to "sweep" behind the party. After that, Sparky never went without light.

It's funny how some of the most delightful aspects of travel-ling are those we would never plan for or expect. I would never have imagined that one of the highlights of our trip with the Cave-man would be a Jack Russell terrier, but it got so we hardly knew what to do without him. The one night that he missed dinner — while romping with Ms Poodle in the under-brush — we had nothing to talk about, chewing in silence, tonguetied in the absence of our one com-panion who lacked language. As one of our fellow travellers said in an interview for Tim's show, "Sparky is my new friend." And that was a wrap.

Tim, proud owner of both beast and genuine feel-good footage, couldn't have scripted it better himself.