An attacker riding pillion shot a 37-year-old Buddhist traffic policeman as he drove to work in Pattani province and a Muslim official was shot dead while riding his motorcycle to collect electricity payments in nearby Yala province, police said.
They were the latest casualties in a spate of violence that has claimed more than 250 lives since January.
"The police killing is obviously linked to the unrest," Colonel Chaiyan Supachaiyakit of Yarang police station said.
"The officer had no personal conflict with anyone. The gunmen just want to wreak havoc in the region," he said.
Police declined to speculate on the motive for the killing in Yala, but said it was not a robbery since the 50-year-old official still had 10,000 baht ($245) cash on him.
The government has alternately blamed bandits, crime bosses, separatists and anti-Western sentiment in the Muslim world for the daily explosions and shootings in the region, home to a fifth of Thailand's 7.5 million Muslims.
Despite sending thousands of troops to bolster security and promising millions of dollars in development aid, the government has failed to stop the unrest in the Malay-speaking region, which borders mainly Muslim Malaysia.
Security officials arrested eight suspects in three separate raids in Yala province on Monday on suspicion of plotting bomb attacks on government buildings and killing officials.
The first five suspects, aged between 19 and 24, were arrested during a raid on a house with a list of security officials they planned to stalk and kill, flashlight and batteries, machetes, mobile phones and some documents, police said.
In January 250 people were killed
in a spate of attacks
"We have much evidence showing that they were preparing for some assassinations of officials," Prime Minister Thaksin Shinawatra told reporters during a trip to the north on Tuesday.
"All the objects we seized may look harmless, but if we put everything together, it is obvious that they were planning some attacks," Major General Tani Twidsi, deputy chief of the southern police bureau, said.
"So far, they have been detained under martial law, but we are collecting more evidence to press formal charges against them." Another suspect, aged 26 and believed to be linked to the first five youths, was arrested late on Monday, police
The arrests came after a remote-control bomb buried on a football field in Narathiwat killed one soldier and wounded six while playing soccer on Sunday.
The bomb was set off as Thaksin was inaugurating a youth soccer league in neighbouring Yala province.
A military report obtained by Reuters said the other two suspects, aged 31 and 39, were arrested while trying to attack an army patrol at a rubber plantation in Yala province with an explosive device which did not explode.
Soldiers found 4.5 kg of C-4 explosive at the rubber plantation and five kg of dynamite at the suspects' house during a dawn raid on Tuesday, the report said.