The bus overturned in the collision, which occurred at 08:00 in the morning, local time, about 50 km east of Bangkok.
The bus was on its way to a temple in Cha Choeng Sao province, two hours outside Bangkok.
- The number of deaths so far is 17, the district police chief told The Guardian.
Early pictures of the rescue work showed dented metal and cabinets.
People lie along the train tracks and their belongings are scattered.
According to authorities, 65 people were on the bus when it collided with the train.