From the linked article the driver claimed: As they approached the railway, Wichai noticed the oncoming train and came to a stop. However, one of the passengers urged him to proceed, assuring him that they could cross the railway in time. Tragically, they could not make it in time, and the train collided with the back of the pickup, where most of the colleagues were seated.
I'm guessing if pressed he will say it was one of the people that died that told him.
The article does go one with another explanation of what might have occured.