http://www.stevevanbeek.com/trips.php.
He is the absolute specialist of the South-East Asian Rivers...and more !
www.coral-hotel.com
A peaceful 3* hotel along a non-touristic coast, 5 hours drive from Bangkok: Bangsaphan village; friendly staff, beach activities, excellent day-trip excursions.
Highly recommended.(French & English speaking)

www.sangtonghuts.com
A lovely place to stay in Mae Hong Son after your rafting expedtion.

www.chiangmai-xcentre.com
Paint-ball, Bungy-jump, buggy-cross...all fun !

www.ActiveThailand.com
Adventure tours in Northern Thailand (Rafting, Cycling, trekking...)

www.clickandtravelonline.com
Bicycle tours in Chiangmai and Northern Thailand