The attack happened about 9am when gunmen on the back of a pickup truck opened fire with automatic weapons at a tea shop in tambon Kehraw's Moo 5.
The victims, all elderly Muslim men, were identified as Chalee Samato, Harong Taba and Tuansoh Waba. A fourth man, Yaya Wayeh, 37, was wounded.
The gunmen also stole three pistols from the deceased.
Police said a separatist group was probably responsible for the attack.
"We had intelligence indicating that insurgents were going to target teachers and soldiers, but we didn't expect them to attack villagers," the Internal Security Operations Command's (Isoc) Fourth Region Forward Command spokesman, Col Pramote Promin, said. Earlier in the day, eight closed-circuit television cameras were set on fire in tambon Ban Rae of Yala's Than To district, police said.
Two rubber tappers were also shot and wounded while working in their plantation in tambon Kala of Yala's Kabang district early Saturday.
The tappers were identified as Charnvit Boonanant and Pornthep Boonanant, both 40. The men were taken to Yala Regional Hospital for treatment.
Meanwhile, about 20 soldiers from Yala Special Task Force 11 raided rubber plantations in Bangoi-jija village Moo 2, in tambon Yupo of Yala's Muang district.
The raids followed a tip-off indicating that a separatist group led by Roki Doloh had stored explosive materials there.
The raids uncovered a 5kg gas cylinder, electrical cords, nails and urea fertiliser.
Four soldiers and four villagers were wounded in a bomb attack in Sungai Kolok municipality area of Narathiwat Saturday.
Police said the explosions took place at 6.20pm.
A bomb planted in a garbage bin exploded at Bonlap intersection in the Sungai Kolok municipality area.