The four separate incidents were the latest in a spate of violence that has claimed more than 200 lives since January, despite a pledge by the government to restore peace to the impoverished region.
Fearing daily attacks, dozens of teachers and other civil servants in the three southernmost provinces have sought permission to own guns. Some have even travelled the 1200 km to the capital Bangkok to buy them, police said.
"Gun shops are getting great business from teachers as many of them have already received a permit," said Major General Paitoon Pattanasopon, chief of Pattani provincial police.
Most of the victims, including those in the last 24 hours, have been attacked by gun or machete-wielding men on motorcycles.
In Yala, police said a 40-year-old Muslim fish vendor was shot dead by a motorcycle-riding gunman while on his way home from market on Tuesday.
In Pattani a Buddhist mechanic was gunned down by two men on motorcycles at his shop late on Monday. A few hours later, attackers threw petrol bombs at a row of houses in a market in the same province, setting fire to three shops and seven stalls.
In neighbouring Songkhla province, a Muslim army captain was shot while driving to work, although his injuries were not life-threatening, police said.
Thai security forces have been
accused of abuses
"The motive is obviously linked to the current unrest in the south," Police Lieutenant Colonel Pravit Chorseng said. "He had no conflict with anyone."
Authorities routinely blame Muslim "militants" for the daily explosions and killings that have revived memories of a separatist insurgency which plagued the region in the 1970s and 1980s.
'War on terror'
But despite sending in thousands of troops and promising millions of dollars in development aid, there has been no let-up in the unrest across the three majority-Muslim southernmost provinces, which have been under martial law since January.
The worst violence came at the end of April when troops and police killed 108 Muslim activists, including 32 in a mosque shootout, prompting accusations of brutality.
Human rights groups say people in southern Thailand feel like the victims of Bangkok's uneven development policies.
They have also accused Thailand of using the global "war on terror" as an excuse to crack down on dissent in its southern provinces.