The accident occurred at a curve in the track just downhill from Ban Hin Lub Station. Middle carriages in the 16-car train derailed, pulling the rest from the tracks.
The cement was being shipped from Saraburi to Chiang Mai.
Wutthikrai Sutthikul, chief of railway management for Area 2, said six freight containers loaded with cement were blocking the track and had to be moved first.
He said the curve needed adjusting to give trains better balance and prevent further accidents.