The on-duty rangers were travelling in a pick-up truck from their base when the bomb exploded on Ban Wang Kran-Pattani Dam Road in tambon Ta Seh at around 7am.
Police suspect an insurgent group led by Roki Doloh set off the home-made bomb in a 10kg cooking gas cylinder.
Meanwhile, Yala police arrested Bonya Saman, 31, who was wanted for his alleged involvement in a gun attack on Bannang Sata police on September 9, 2009. He reportedly fled the area and had laid low before returning to Bannang Sata. He was arrested in a house in the district.