Headless Ghost

Pakdee is a reporter who happens to witness a car accident that lead to the death of the driver by decapitation. He starts acting funny and is hung up on deaths of people whose heads were cut off. His boss starts to complain about his work but it soon improves when he begins covering a spate of murders by decapitation in Bangkok and he even gets an award for his reporting. But he is still acting strange. What's going on? Is he haunted by the ghost from the car accident? Does he know more than he says about these deaths?