Authorities in the border provinces are looking for a vehicle, one of five stolen from Songkhla which they suspect may be carrying explosives and could be heading to Yala.
The security forces were on the lookout for a golden-bronze Isuzu pickup truck which was thought to be carrying a fake licence plate. It is thought to be one of five vehicles stolen from a used-car showroom by 6-7 robbers in Songkhla's Na Thawi district on Wednesday.
The other four vehicles have been located. One of them, a Toyota pickup truck, exploded near a bridge in tambon Yabee, injuring four army soldiers in Pattani's Nong Chik district around 2.30pm.
The four soldiers were attached to a mobile medical unit. They sustained minor injuries in the blast and were rushed to the hospital in the Inkayutthaboriharn army camp in Pattani.
Police said they were investigating if the robber who drove the pickup had fled the scene or whether he or she had died in the blast as the force the explosion had left the vehicle badly wrecked.
Another stolen vehicle, a Mitsubishi sedan, was found abandoned after it ran out of petrol along the road in Thepa district of Songkhla. The robber who drove the sedan took one person hostage. He exchanged gunfire with the authorities, injuring two people, before fleeing.
Also in Thepa district, another stolen vehicle, a Phatthalung-registered Isuzu pickup truck, was driven through a roadside checkpoint in tambon Pakbang.
Security officers gave chase and traded gunfire with the driver.
The driver later escaped from the pickup which was found to to be laden with explosives. Bomb disposal experts were called to make the vehicle safe.
The last vehicle recovered was another Isuzu pickup truck carrying a Bangkok licence plate. It was found abandoned near a rubber plantation in Ban Kang in Khok Pho district of Pattani on Wednesday afternoon.