A former MP for Narathiwat on Wednesday denied involvement in the car bombing that injured seven people on Koh Samui on April 10, as investigators arrested another suspect in Pattani province.
Najmuddin Uma, a former Matubhum MP, told reporters at a hotel in Muang Narathiwat district he had nothing whatsoever to do with the bombing.
He had already filed a defamation complaint with local police over allegations that a political faction had teamed up with southern insurgents to set off the bomb and discredit the government.
Mr Najmuddin said he was implicated when a picture of him with Masae Useng, leader of the BRN-Coordinate insurgency group, was posted online.
The photo had been taken in 2000 when he, as a former MP, took leaders of local communities and administrative organisations on a field trip to Phuket. Masae Useng had been a member of the Tambon Juap Administrative Organisation in Cho Airong district of Narathiwat at the time, Mr Najmuddin said.
The politician is a member of the Wadah faction active in the far South.
On Tuesday security officials arrested an auto broker in the southern province of Pattani in relation to the car bomb explosion.
Abdulroning Dueramae, 51, was detained at his house in Sabarang sub-district of Muang Pattani district.
He is suspected of buying vehicles from a used car dealer identified as Bang Yi, or Bae Li, in Pattani for use by the car bomb team that set off the bomb in the car park of the Central Festival Samui mall, a security source said.
Mr Abdulroning admitted that he knew Abdulrasa Dumeedae, the 52-year-old driver for La-ae tambon administrative organisation whose Mazda pickup truck was used in the car bombing on Koh Samui, the source said.
He also admitted to knowing Pattani teacher Sabidi Salaebing, 33. Mr Abdulrasa and Mr Sabidi have already been detained for interrogation in relation to the car bomb attack.
Mr Abdulrasa earlier told police that a group of people had robbed him of the pickup truck in Yala on March 31. However, witnesses said they saw him talking to two men at the "robbery" scene before reporting the loss of the truck to police.
Bang Yi, or Bae Li, recently left Thailand, supposedly on a pilgrimage to Saudi Arabia, after selling three vehicles to the car bomb team, the source said.
Earlier Prime Minister Prayut Chan-o-cha said the attack could have been motivated by either a political or business conflict, and he ruled out a connection to the southern insurgency.
Police spokesman Prawuth Thawornsiri alleged on Wednesday that Mr Abdulroning had acquired three vehicles on behalf of the bombers -- a silver Honda Civic registered in Bangkok, a four-door white Mitsubishi Triton pickup truck registered in Chon Buri and a four-door Isuzu D-Max pickup truck registered in Bangkok that were used to carry the bombers and prepare the attack on Koh Samui.
Pol Lt Gen Prawuth expected that information from Mr Abdulroning would lead police to the mastermind of the attack.
The police spokesman said police would seek warrants for the arrest of about six more suspects in a few days. Some of them involved offences against national security.
"Officers are giving weight to a political motive to create a "situation". There is not enough weight or motive for any expansion of the insurgency movement in the three southern border provinces, but an experienced group active in the South might have been hired for the bombing for another purpose," Pol Lt Gen Prawuth said.
One of the nearby vehicles damaged by the car bomb explosion in the Central Festival Samui car park on the night of April 10 (Bangkok Post file photo)
