Police were notified of the accident just after midnight and called for help from firefighters and rescue volunteers.
The trailer was almost entirely engulfed in flames after its petrol tank exploded, and the man and woman trapped inside could not be pulled out until firefighters were able to get the flames under control. They are severely burned and being treated at Nadee Hospital.
Their month-old infant was found dead on the road. Police believe the three were a family and the infant flew out of the windscreen when the trailer flipped.