In a bloody day on Wednesday, two militants were killed and two policemen wounded in a shootout at a house in the Raman district of Yala province.
Shortly afterwards a 56-year-old janitor and his 11-year-old son were shot dead by unknown assailants in an ambush in the same area as they travelled back from school.
"The janitor's nine-year-old son was also critically wounded in the attack," the police statement said.
Raman is a militant stronghold, or "red zone", which is frequently rocked by attacks targeting security forces or locals accused of collaborating with the Thai authorities.
Later Wednesday two Buddhists, a 28-year-old woman and 47-year-old man, died as militants sprayed bullets into the crowd at a local festival in Sai Buri, Pattani province, also wounding four others.
The deaths marked another grisly day in Thailand's eight-year insurgency which has left more than 5,300 people dead in the kingdom's three southernmost provinces of Pattani, Yala and Narathiwat.
A surge in violence since the summer has prompted Prime Minister Yingluck Shinawatra to pledge to redouble efforts to end the conflict.
The militants are rebelling against a history of perceived discrimination against ethnic Malay Muslims by successive Thai governments and alleged rights abuses by the army.