Another man was killed minutes later in a drive-by shooting in the province's main town.
Police also said that at least six men in a lorry later stormed into a home in a nearby district, opening fire on a family of five.
Two men and a woman aged between 33 and 62 and a 16-year-old girl were killed, while a 13-year-old girl was injured.
Police also believe the same group killed two other Muslim men found dead at a nearby prayer house.
Mosque attack anniversary
The incidents came before Tuesday's anniversary of the April 28, 2004, assault on the Krue Se mosque in Pattani province by Thai security forces.
At least 32 Muslim fighters taking shelter in the mosque died in a hail of rocket-propelled grenade and assault-rifle fire.
Other clashes on the same day resulted in the deaths of 107 people turning the mosque attack into a symbol of what many Muslims in Thailand's south see as the heavy-handed tactics of the Thai authorities.
The raid, condemned by human rights groups, fuelled an insurgency in southern Thailand that has claimed more than 3,400 lives.