In a separate attack, two people, a villager and a defence volunteer, were shot dead in the Bacho district of Narathiwat province on Saturday, officials said.
The victims were on a hunting trip when four suspected fighters chased them and opened fire, Lieutenant Thanapong Puengsak of the local police said on Tuesday.
Local residents are often hired as armed auxiliaries to the regular military.
Pattani and Narathiwat, along with Yala, are the only Muslim-majority provinces in the Buddhist-dominated country.
The attacks took the number of deaths in the region to 19 in the last 10 days, with more than 60 people wounded.
The fighters target civil servants and others working with the government, including soldiers, police and informants.
Attacks on civilians are thought to be intended to scare the Buddhist community into fleeing.
Yala, Pattani and Narathiwat were part of a Malay Muslim sultanate until annexed by Thailand a century ago and separatist tensions have simmered ever since.
Local Muslims largely oppose the presence of thousands of police, soldiers and state-armed Buddhist guards, whom many suspect of carrying out extra-judicial killings.
The authorities deny the allegations.