The four insurgents were identified as Wankhoyari Sarayoraseh, 25, Abdulhalem Jehkhu, 25, Paming Jehkhae, 30, and Muhamad Mudolasae, 27, all of Narathiwat province.
The reports said intelligence units had warned security forces they might try to sneak into the towns during the New Year festival to lay bombs.
In response to the warning, combined forces of military, police and defence volunteers have set up checkpoints on routes leading to Hat Yai.
On Wednesday, Deputy Prime Minister Chalerm Yubamrung, as head of the operations centre for solving problems in the three southern border provinces, said he would today hold a video conference with village and tambon chiefs and governors in the area to lay down an operational guideline.
On Jan 7 he would make a call on the Chularatchamontri, the Thai Muslim leader, before leading the National Security Council (NSC) chief, director of the Southern Border Provinces Administration Centre (SBPAC) and commander of the Special Branch Police to Malaysia for talks with officials there on ways of solving problems in the restive South.