The train was carrying almost 300 passengers when seven carriages went off the tracks in the northern Denchai district at 3am. The train was headed to the hill resort town of Chiangmai.
Eighteen tourists from Australia, France, Spain, Japan and the US suffered minor injuries, the Nation daily reported.
Most of the passengers were asleep at the time of the accident.
"Derailments happen quite often," State Railway of Thailand Governor Prapat Chongsanguan was quoted as saying by the newspaper.