Holding dialogue with one Muslim insurgent group could prompt retaliatory attacks by others as a show of strength, Deputy Prime Minister Yutthasak Sasiprapa said.
"I want to insist that the government has no policy to get involved in peace talks," said Yutthasak, a military general who oversees national security.
Suspected militants set off a series of car bombs in the far south on Saturday that killed 15 people and wounded hundreds.
In the town of Yala twin blasts killed 12 people and wounded more than 100, while a car bomb at a hotel in the city of Hat Yai triggered a fire that killed three people and injured more than 400, according to a new official toll.
The attacks marked an apparent escalation of a shadowy insurgency, without clearly stated aims, that has claimed thousands of lives since 2004.
The near-daily bomb or gun attacks are indiscriminate, targeting both soldiers and civilians, Buddhists and Muslims.
Thailand's army chief General Prayut Chan-O-Cha said Monday that more than 3,000 Muslim militants were involved in the violence.
The insurgents are not thought to be part of a global jihad movement but are instead rebelling against a long history of perceived discrimination against ethnic-Malay Muslims by successive Thai governments.
A state of emergency is in force in the worst-affected areas of the region, which rights campaigners say in effect gives the tens of thousands of military troops based in the area legal immunity and fuels rights abuses.
The governor of Songkhla province, where Hat Yai is located, on Tuesday offered a reward of 500,000 baht ($16,130) for information leading to the arrest of each of two suspects in the hotel blast filmed by security cameras.