Police Col. Tuanday Juthanan says four militants opened fire with M16 rifles in front of a grocery store in Pattani city on Wednesday night.
He says the attack killed six people, all Buddhists, and injured another man. It wasn't immediately clear why they were targeted.
Tuanday says the attackers fled on two motorcycles and dropped nails on the road to prevent security forces from pursuing them.
More than 5,000 people have been killed in Thailand's three southernmost provinces since an Islamic insurgency erupted in 2004.
Attacks occur almost daily in the Muslim-dominated sub-region despite recent government efforts to hold peace talks with the militants.