Where to eat & stay
Most places of interest can be found within walking distance of the clock tower intersection on Thanon Banphaprakan. Pubs and bars line Thanon Chet Yot south from the clock. There's more open-air dining and drinking around the night bazaar close to the bus station off Thanon Ratanaket.
Muang Thong Phattakan (Thanon Phahonyothin, near Wiang Inn, 0 5371 1162, main courses B 60) is a bracingly authentic Chinese-Thai khao tom (boiled rice soup) shop.
Grander Salung Kham (No.834/3-4, 0 5371 7192, main courses B98) dispenses grilled meats and northern dishes.

As for accommodation, the Wiang Inn  is functionally pleasant, while Golden Triangle Inn  is a quiet, leafy compound. This is not a budget town but
Chian House has large rooms and a small pool on a quiet island suburb. You need transport to enjoy the Thai design and gardens of
Rimkok Resort  across the river, or the remote 'luxury bamboo'
Phu Chaisai Resort & Spa (26 kilometres/16 miles north of Chiang Rai, 0 53918333). It offers hilltop views from the baths in its love-nest villas.
Mae Sai & around
The town centre is divided by a highway ending at the narrow bridge into Tachileik in Shan State, Burma. Mae Sai offers little that's respectable apart from views at Wat Phrathat Doi Wan, myriad jade workshops and some river guesthouses. Shops and stalls selling tapestries, puppets, cheroots and other Burmese goods fill the market by the checkpoint, which you may cross for $5 (if open) into greener (but grimmer) Tachilek, with its new Rangoon-style chedi and rare animal parts brazenly on sale.
Trekking
Most visitors to the north take some kind of trek or 'soft adventure' - with typical components being hiking, bamboo rafting, elephant riding and visiting hill tribes (some people stay in village homes for up to a week). It can be fascinating (if voyeuristic), but 30 years of cut-rate trekking and the desire to see authentic (poor) villages has done little to help the hill tribes.
Eco-tourism is touted as a remedy, although many of the countless operators in Chiang Mai, Pai, Mae Hong Son, Thaton and Chiang Rai pay lip-service to its principles. When choosing, check your specific guide's knowledge of tribal ways and language.
A positive force is the Population & Community Development Association (PDA), which is formalising arrangements with a B40 fee to enter the Akha village of Ban Lorcha (Highway 1089 km53, 20 kilometres/12.5 miles north of Ban Thaton). Entrance is during the day, 8am-5pm. The money goes into funds for village development and to replicate the project elsewhere. There are signs in the village instructing visitors to ask permission (through gestures) before taking photographs and to desist if refused. Similarly, ask before entering houses, don't step on the doorsill (home of house spirits) and remove shoes if the floor is raised. Changing clothes, showing nudity or public intimacy are deemed offensive. And even if beer and liquor are sold, drinking it only emphasizes the gap with villagers who can't afford it. Handing out gifts or money encourages begging, so it's best if the guide distributes such items fairly.
Where to eat &stay
Mae Hong Son Guest House (295 Thanon Makasanti, Mae Hong Son, 0 5361 2510, rates 13600-13900) liaises with a co-operative of freelance guides committed to community based tourism. PDA Tour (620/25 Thanon Thanalai, Chiang Rai, 0 5374 0088, B2,50084,800) hires Akha and Lisu guides and supports responsible projects like Ban Lorcha. Book well ahead for specialized ecotrekking with Natural Focus (129/1 Thanon Pa-Ngiw, Chiang Rai, 0 5371 5696). When trekking, warm clothing, torch, insect repellent, toiletries, towel, a water bottle and supportive footwear are musts - and maybe bring a sleeping bag.