For the young and adventuresome, a dirt bike (mountain bike) can offer extensive freedom. By local standards, it's a real expense: about B500 a day rental. Three or four people could hire a car and guide for about the same per person. 100cc "Lady Bikes" (Honda Dream or Suzuki Crystal) are usually B150/day, use less gas and similarly offer a variety of interesting choices. There's even a small highway along the Burmese border, not recorded on maps but easily accessible with almost any vehicle. Rental is easy - you put your passport on deposit. Soon Motorcycle at 197/2 Trirat Rd., tel 053-714068, and St. Motorcycle (jeep and car) at 1025 Jet Yot, tel 053-752180 or 713652, offer old Dreams for B150/day, new for B200, and 250cc Hondas for 5-600/day).
Bicycling: the capitol city and much of the northeast of the province are great for cycling. Chiang Kong, Chiang Saen and Mae Sai are easily accessible, as are Khun Gon Waterfall, the Mae Lao Zoo and towns to the south along 118. The Wawi Valley area is excellent for mountain biking, and good bikes for rent can be located readily. B80/day at Pure Power Internet on Ratanaket Rd. north of Pratu Siri Intersection, 053-752184 or 714619; B100/day at Soon Motorcycle, 197/2 Trirat, 053-714068). Karekaron Books at 869/18 Pahonyothin, 053-753172, just south of Pratu Siri, has mountain bikes from B60 (old) to B100 (new) per day. Or ask at Teepee Bar, just north of there (towards the stoplight).
Horse riding: Mae Salong Outdoor stables at Ban Mae Salong Nai, west of Mae Chan (33 kilos north of Chiang Rai and 9 km. west of the highway - 270 Mu 4, E-mail: semokstables@yahoo.com). Tel 01-882-5509. 1 hr/200B, 1 day/B2000. English speaking guides. 2-3 day excursions available, also target shooting and camping.
Joe's Horse Club, just off Rt 118 near Mae Suai offers half and full day riding tours, riding lessons, and horse rental by the hour for experienced riders. Tel 053-786039 or 01-7169303. 8 horses.
River Trips:

Public boats to Thaton leave 10:30 am, take four hours and cost 200 baht per person before the recent gas price rises. The return trip leaves Tha Ton about 12:30 pm, same price and time extent (maybe a little longer when the river is low or moving fast). Long-tail boats can be hired privately for trips to the Buddha Cave, Ban Ruam Mit elephant camp and the near-by hot springs (B700 for a boat, which can carry up to 7 or 8 people, depending on their size. It's about an hour going upstream; quicker returning). Going by river to Chiang Saen is not posible, though, as there's a dam about 4 kilometers downriver.
One can boat trip up the Mae Nam Khong (Mekong) to Sipsongpanna in Yunnan, China (on apple boats, from Chiang Saen), or down to Luang Prabang (smaller speed-boats for eight people and luggage, from Chiang Khong).
Mekhong River trips - Chiang Saen to the Golden Triangle River Confluence takes about half an hour. Going down to Chiang Khong takes an hour and a half, depending on current and water level. Prices can depend on the season, and on group size.