The army has tightened security along the Sungai Kolok River that lies on the border with Malaysia after ethnic Malay suspects allegedly entered Narathiwat to carry out bomb attacks last week.
Soldiers have been deployed along that section of the Thai-Malaysian border in Narathiwat's Sungai Kolok district.
The move comes after an investigation into the multiple blasts in the district last Friday.
Police believe ethnic Malay suspects on a motorcycle colluded with local militant suspects in launching the attacks.
The militants directed the alleged Malay suspects to the bomb locations.
A source close to the probe said the suspects were captured on surveillance cameras heading to a warehouse on a bypass road in tambon Pasemat where a bomb went off which left three people dead and eight injured.
The police probe has also linked the bombings to the alleged smuggling of items, believed to be explosives, from a Malaysian border town into Sungai Kolok.
Police have set up roadside checkpoints to search for the suspects.
Meanwhile, national police chief Pol Gen Somyot Poompunmuang yesterday said security in the far South has generally improved compared to last year.
However, the bomb attacks have prompted security officers, especially those in the business district of Hat Yai in Songkhla, to step up surveillance operations.
National Security Council secretary-general Anusit Kunakorn said development projects in local areas are helping to restore peace in the region, but people must also come out and condemn violence in their communities.
Meanwhile, two paramilitary rangers were wounded by a roadside bomb yesterday morning near a local school in Pattani's Yaring district while providing security for teachers, police said.
The teachers were unhurt as the blast hit the officers' patrol car which was leading the group along Phumi-Muang Wan road.