The route was closed since Sunday morning after the international luxury train from Singapore, the No 952 Eastern & Oriental Express, jumped off the track in Ban Pong district of Ratchaburi en route to the River Kwai bridge in Kanchanaburi province.
Two Japanese tourists on board were slightly injured. They were admitted for treatment in Bangkok.
Old sleepers were blamed for the derailment of two carriages of the seven-carriage Eastern & Oriental Express and its locomotive.
SRT said repair of the damaged rail line has been fixed last night and the first local train from Nam Tok station to Thonburi was allowed to resume service last night.
Two other weekend tourist trains stranded at Nam Tok station Sunday also returned to Bangkok with empty bogies last night.
The Kanchanaburi route is popular with local and foreign tourists as one of its section from Kanchanaburi to Nam Tok station in Sai Yok district is dubbed the the “death railway”.