As a Peace Corps volunteer teaching in northeastern Thailand's parched Khorat Plateau, I spent much of my time dreaming of limestone cliffs, caves and bejewelled waters. I stayed up late re-reading the island chapters in the Lonely Planet guide, figuring that the best places were the ones that were given just a paragraph or a sentence. Whole pages devoted to one area meant two things: tourists and high prices. On my school breaks, I stuffed a couple of T-shirts, my swimsuit, snorkel and sarong into my daypack and hopped buses, trains, vans and boats for the distant islands. I travelled with an obsession, a need to find exactly what I was looking for — the perfect combination of local people, boats, marine life, and beautiful scenery. Sometimes I confounded myself. Here I was on pristine beaches with only a scatter of cheap bungalows, thinking, This isn't quite what I wanted. One island was too desert, there was nothing to eat. Other areas had too many tourists and too-Westernized food. Don't get me wrong. There was a thrill to my Quixotic questing, so I didn't complain much — in fact I bragged of my adventures to friends back home. But of pure satisfaction, I found little. That is, until I discovered the islands of Trang.

Trang is the province lying just south of Krabi. Serviced by an airport, train station, and bus terminal, it's just as easy to visit as the more-popular Krabi, yet it receives far fewer tourists.

The more than 100 islands of the Trang Archipelago are divided into two groups: the southern Petra Island National Marine Park, and the northern Haad Chao Mai National Marine Park, with the whiter beaches and greater environmental challenges. Haad Chao Mai National Marine Park is headquartered on the mainland, near the town of Pak Meng, and its borders include a number of beaches and caves in addition to 47 islands. Passenger boats leave from Pak Meng or Kuam Gum Ku, depending on which bungalow resort you've signed up with. Generally, you needn't reserve a room, but the easiest thing is go with a tour company in town, across from the railway station. Or you can book online, but most resorts here have no websites. Bungalows are available on Koh Muk, Koh Ngai, Koh Kradan and Koh Libong, and the national park stations on Koh Kradan and Koh Rok have tents.

The island that hooked me was Koh Muk (or Mook), which translates as Pearl Island. It was someplace real, where real people lived real lives. The first morning, we filmed sunrise over the mountains of the mainland, explored the village, the eastern beaches and mangrove forest, then trekked west to capture the sunset at Haad Farang Beach. The path snaked through a rubber plantation before opening on a field with a house and a handful of thatched huts. Grass and trees ran to the edge of the sand, a wild beach unsullied by development. A 50-foot sailboat swung on its anchor in the dying breeze, and a young couple motored their dinghy to shore along a golden road laid by the setting sun. Black volcanic rock halted the march of fine sand before the limestone formations sealed off the cove. Craggy islands jutted from the smooth water just a short way off. As we placed the tripod in the sand and set the camera, I knew I had arrived. This was it.

The villages of Koh Muk are Muslim, with roughly 5,000 souls dressed in traditional sarongs and headcoverings. Everyone seemed to be either fishing, mending nets, drying fish in the sun or building or painting wooden boats.

And real people mean real food. Local curries, grilled fish, fresh squid — all of it at village prices. During both my first visit and my 2000 and 2004 returns, I sat and talked for hours with the fisherfolk, played football with the young men in the late afternoon. When I stepped on a spiny sea urchin, the jolly big man at the fish market squeezed lime on my wound and advised me to pee on it. The acid would kill the poison and help the spines work their way out. In the evenings, I returned to his market for seafood feasts, including a barracuda cooked four ways in such quantity that five adults couldn't finish it, all for under 300 baht.

My friends and I took boat trips to the surrounding islands, snorkelled off Koh Maa, where red, violet and yellow soft corals proliferate in the shallowest of depths, and schools of colourful fish swirl through the clear waters. Off Koh Kradan, we watched the largest lion fish I've ever seen — nearly the size of a rugby ball — hover in the shallows, rotating slowly to feed. Herons, terns and brahminy kites dove for fish. The first wild sea turtle I ever saw surfaced near our boat on the ride back to the mainland.

We also swam the tunnel of the Emerald Cave, where the sun reflects the water, deep green against the walls. The swim leads into absolute darkness, but, within 30 seconds, pale sunlight reappears. The interior lagoon is an open cavern, or hong, left by the collapse of a massive cave, a cylinder lined by limestone cliffs with a smooth, sandy beach and a patch of jungle against the walls. As with many places of great beauty, the Emerald Cave is now a hotspot for regional tourism, with boats ferrying in hundreds of visitors daily. Unless you arrive early in the morning or late in the day, you won't see much but bobbing orange lifejackets and flashing digital cameras.

In 2003, the Tourism Authority of Thailand (TAT) launched its "Unseen" programme to promote out-of-the-way destinations. The Emerald Cave is featured among 30 sites around the country, guaranteeing more tour groups — and more trash left in their wake. Prior to the annual mass underwater marriage at Koh Kradan, where about 30 couples were married on Valentine's Day, divers cleaned over a tonne of rubbish from local reefs and the Emerald Cave.

Thanks to the Yadfon Association, a local non-governmental organization (NGO), villagers along the coast of Trang have been working together to conserve resources and protect traditional fishing grounds from the wildly destructive shrimp farms and the big factory trawlers that have wreaked so much havoc on the ecosystem over the past 40 years. Founded in 1985 by Trang native Pisit Chansnoh, his wife and two friends, Yadfon means "raindrop", a name chosen because "rain is fair to everyone". In 1992, Yadfon teamed up with the international Mangrove Action Project. As one Trang fisherman is quoted on the MAP website as saying: "If there are no mangrove forests, then the sea will have no meaning. It is like having a tree with no roots, for the mangroves are the roots of the sea."

For nearly 20 years, Yadfon's grassroots outreach has been helping to educate and empower fisherfolk, Trang's poorest people. Now villagers help enforce the 3,000-metre coastal fishing limit, foster community management of mangrove forests, and work to restore seagrass and coral. Villagers have agreed to stop eating turtle eggs and dugongs, a manatee-like sea mammal. They practise more sustainable fishing practices and have forced middlemen to pay fairer prices for their catch, as well as fuel suppliers to stop grossly overcharging. There are nine community-managed mangrove forests in Trang, and some fishing villages have enjoyed increases of as much as 40 percent. Yadfon supports "development according to local culture", as opposed to the modern economic developmental models that tend to be favoured by governments. In 2002, Pisit Chansnoh won the Goldman Environmental Prize, the Nobel of conservationism, which includes a purse of US $125,000.

On my latest trip to Koh Muk, in February, I discovered the first major changes since 1996. The valley and open field of Haad Farang has been practically filled with bungalows. The largest of four or more operations has expanded to Phi Phi proportions, and is, in fact, owned by the same people who own prominent resorts there. The bungalows are reasonably priced, clean and sturdystructures serviced by a restaurant, dive centre and beach bar.