"His body was totally torn apart," the AFP news agency quoted Major General Wichet Visaijorn, a southern army commander, as saying.
There was no immediate claim of responsibility for the attack, but the army blamed separatist fighters.
"The militants staged this violent attack to draw attention," the southern commander said.
"We are in control of the situation. Small attacks are common during visits to get attention and publicity."
Violence in Thailand's Muslim-majority Yala, Narathiwat and Pattani provinces has claimed more than 3,600 lives since January 2004.
The Thai government has made little progress towards quelling the unrest despite deploying thousands of paramilitary troops - usually residents hired as armed auxiliaries to the regular military - in the area alongside at least 30,000 army troops.
Muslims make up more than 90 per cent of the two million people in southern provinces of Yala, Pattani, Narathiwat and Songkhla.
Many complain of being treated as second-class citizens in mainly Buddhist Thailand.
The area was a semi-autonomous Islamic Malay sultanate until annexed by Thailand in 1902.
Several violent uprisings have been put down by the army over the century.
The latest uprising flared in January 2004 when fighters raided an army base, killing four soldiers.
Despite martial law imposed in 2004 and tens of thousands of military or paramilitary troops in the region, frequent attacks blamed on Muslim fighters have left more than 3,700 people dead.
Abhisit met members of the government-backed civilian militias on Thursday in Yala, where he pledged to freeze the number of troops in the region.
"If we want to restore peace that cannot be achieved by deploying enormous forces from outside the region," he said.
"At least this year the government will freeze forces and by 2012 troops will start to reduce."
The prime minister also announced a $60m stimulus package for the region to help double the average annual income in the area to nearly $4,000, AFP reported.
He also called on militia members to work with local residents to prevent rights abuses, which he said, separatists could use as a pretext for more attacks.
The group or groups believed to be behind the attacks have made no public pronouncements but are thought to be fighting for an independent Muslim state.
Tensions have simmered since the region, formerly an autonomous Malay Muslim sultanate, was annexed by predominantly Buddhist Thailand in the early 1900s.
The region's Muslim population have also long complained of discrimination by the central government.