A defence volunteer and three civilians, one a young child, were hurt when gunmen opened fire and threw a bomb at a checkpoint in Sungai Padi district on Thursday night.
The attack occured around 7.30pm on Jarusathian Road in tambon Paluru, said Pol Capt Theerapong Phimpha, deputy investigation chief at Sungai Padi police station.
The assailants fired many shots at the road checkpoint and then threw a bomb.
Four people were wounded, including a one-year-old girl.
Those injured were defence volunteer Manawee Kotae, 37, and three local residents Chalermphol Phuenpa and Phattrawadee Phromchuen, 37, and her young child Varida.
Police blamed southern insurgents.