The insurgents exchanged fire with railway guards before fleeing the scene, Police Col. Dulyaman Yaena told AP.
The explosion occurred in Tue So district of Thailand’s Narathiwat province, causing a disruption to train services.
All the injured were hospitalized.
The attack was a second for the weekend. In the first incident one person was killed and 20 were wounded after a motorcycle bomb exploded in southern Yala province.
More than 5,000 people have been killed, since the escalation of Muslim insurgency in 2004 in Muslim-dominated southern provinces.
The conflict has been ongoing for a decade between local Muslim militants, who want a separate state, and the Buddhist-dominated Thai army and paramilitary forces.