During the eight-day trial, which coincides with Khmer New Year, Royal Railway will operate a daily service in each direction, departing from Phnom Penh and Sihanoukville at 07.00 with intermediate stops at Takeo and Kampot.
The journey time for the 264km trip will be around eight hours with a $US 7 single fare. One of the two trains being used for the service will include air-conditioned coaches.
Freight trains returned to Sihanoukville at the end of 2012 following the completion of a rehabilitation project, which was funded by the Asian Development Bank.
In January the Cambodian government said it expected to restore its rail link to Thailand by the end of this year.