About 500 miles north of Bangkok in the Mae Ping River Basin sits a twist of jungles, national parks, and mountains populated by hill-tribe people. Chiang Mai, Thailand's second-largest province, also hosts the country's highest peak, Doi Inthanon, 8,448 feet high and the namesake of one of the country's best national parks for hiking. Here in the Doi Inthanon National Park (www.dnp.go.th/parkreserve/asp/style1/default.asp?npid=1&lg=2), you'll find some 360 bird species, including the endemic green-tailed sunbird, as well as orchids and waterfalls such as the 853-foot-high Mae Ya cascade. Wild Thailand Adventure Holidays (www.wildthailand.com; info@wildthailand.com), and similar groups offer five-day treks through this region that also visit the Hmong, Karen, and Lahu hill-tribe people. Often treks into the folds of these mountains involve riding on elephants, perhaps mountain biking, and poling bamboo rafts along cool rivers. Though the company says it charges about $675 per person for a group of two for a five-day trek, during the shoulder season you should haggle to get that down. Alternatively, if you get more people together, the trip drops to as low as $375 per person.

But back to that mountain-biking bit: Rolling through the high jungles of northern Thailand on a fat tire is becoming increasingly popular. From Doi Inthanon you can tackle technical singletrack and forest roads to Ob Luang Gorge via Mae Chaem. Better yet, hook up with Active Thailand (+66.53.277.178; www.activethailand.com) and spend four days cycling about 30 miles a day along paths and dirt roads through the Chiangdao Hills to the Maekok River. Along the way you'll pass through the villages of Lahu, Lisu, and Akha, and cool off with swims under waterfalls. Tours start at $330 per person, but again, try haggling in the shoulder season.

As for digs, the Baan Klang Doi guesthouse (www.baanklangdoi.com) sits within the national park, about 30 minutes outside Chiang Mai, and has deluxe suites with wood balconies overlooking a swimming pool. The complex has a spacious living room, a pub, and a restaurant, and in the shoulder season prices drop by nearly half, from $64 to about $38. Or for a few baht more, during the shoulder season you can book a cottage for $90 a night and get the second night for free.