In Yala's Kabang district, a seven-man squad of special operations police on four motorcycles was hit before noon while escorting teachers.
Lance Corporal Sarawuth Choothanom was pronounced dead at a hospital, while the patrol leader Lieutenant Montree Phummorradok was sent to a hospital in Songkhla.
An Explosives Ordnance Disposal (EOD) officer said a 5kg bomb was packed in a fire extinguisher and put in a fertiliser sack. It was detonated by a two-way radio.
In Narathiwat's Muang district, a military transport truck carrying three Army paramilitary rangers was targeted by bomb fixed to a motorcyle parked by a main road.
The blast killed Siri Jiaranai, who was pronounced dead at a hospital, and wounded the other two soldiers including team leader Sgt-Major Sanya Phromephetnil.
Sanya said the truck was transporting several barrels full of petrol to a ranger base in another district, but the blast did not ignite any of the barrels.
EOD personnel said the 10kg bomb was detonated by a two-way radio.
Police said that insurgents stole the motorcycle used in the attack from a 62-year-old woman on Tuesday after shooting her dead and then repainting the bike blue.