The first bomb went off on the old Highway 42 in tambon Jor Kueyae of Saiburi district.
The bomb was in a steel box and was detonated remotely as a patrol of eight paramilitary rangers providing security for teachers passed by. Ranger Wattana Chan-orn was injured and rushed to hospital.
Another bomb exploded on Road 4071 in tambon talomaena of Thung Yang Daeng district.
A 15-kilogramme bomb inside a fire extinguisher exploded as a police patrol in a pickup truck passed. The truck was wrecked and the four policemen rushed to hospital.
The injured were identified as Pol Sgt Maj Boonsong Gunnaroj, Pol Sgt Maj Adithep Nookongkaeo, Pol L/C Tasmisi Sani and Pol Sgt Boonrit Bangsri.
Police blamed insurgents for both attacks.