Leaflets with messages aimed at extorting money from motorists in Yala's Bannang Sata district have piqued police interest after it was found they were distributed one day after an interprovincial bus was torched in the district on Sunday.
The leaflets, which threatened to harm drivers if they did not pay "road fees", come as police investigate whether those responsible for the arson attack may be linked to the insurgency in the deep South.
National Security Council secretary-general Wanlop Rugsanoh yesterday did not say the two crimes were connected but said officers should look into the motives behind them.
The leaflets contained no clues as to the identity of the culprits and were "not written in Jawi [as with other insurgency-related crimes]", the general said.
The Jawi language is commonly used among Muslims in the southernmost provinces.
An initial examination of the leaflets led police to suspect the extortion attempt may have nothing to do with the insurgency, although the perpetrators may be keen to make it seem like they are, Yala police chief Pol Maj Gen Kritsada Kaeochandi said, without explaining.
Gen Wanlop admitted the two events may have "reduced people's confidence", and promised to tighten security during the New Year period.
The Sunday attack targeted a double-decker bus run by Siam Transport Co. The bus, with 11 people, including the driver and attendant on board, was stationary when a group of men set the vehicle on fire. A similar incident in which a bus was set on fire occurred in 2014, with the same bus driver Abdullah Sabaebo and bus attendant Marorwe Ding. Both work for Siam Transport Co.
Nobody was hurt as the attackers allowed people to disembark before torching the bus.
According to a source close to the investigation, officers have detained four suspects over the arson attack.
One is the owner of a shop selling bottled fuel oil, while the other is a woman suspected of giving clothes to the attackers to change into to help in their escape.