The attack happened at 7:50 am on a road in Tambon Sabarang in Mueang Pattani district.
Polices said the bomb was assembled in a pipe and it was detonated with a walkie-talkie.
An insurgent, who was hiding nearby, detonated the bomb when they spotted the team of policemen arriving at the spot. Fortunately, the three policemen were not hit by shrapnel. They only suffered from chest pain and ringing ear.