CCTV recordings show the pickup truck used in the car-bomb attack at Central Festival Samui shopping mall on April 10 had left Yala just a day earlier and it also stopped for a long period along the Songkhla-Nakhon Si Thammarat border.
An informed source said the pickup, which was converted into a vehicle bomb, had moved from Yala to Songkhla and then to Nakhon Si Thammarat before heading to Surat Thani where the shopping mall is located.
"But along the way, it must have definitely made a long stop somewhere in the border zone of Songkhla and Nakhon Si Thammarat," the source said.
According to this source, recordings showed that the vehicle was sighted on the border of Songkhla's Ranot district at 5.32pm on April 9 and later at 1.05am on April 10 in Nakhon Si Thammarat's Chien Yai district - a spot just a little over 30 kilometres away.
"Officials will have to find out where this vehicle stopped and what happened to it during the period," the source said.
Nakhon Si Thammarat's police chief, Maj-General Kiatipong Khao-sam-arng, yesterday confirmed that relevant officials were looking into the disappearance of the vehicle from security cameras for six hours.
Thaworn Senneam, a former deputy leader of the Democrat Party and co-leader of the People's Democratic Reform Committee, separately said he had received information that those involved in the bomb blast had checked into a hotel in Nakhon Si Thammarat's Khanom district.
"We believe explosives were planted in the vehicle at the hotel," he said.
Thaworn also hinted at the possibility of a police colonel getting involved in this case.
"This police officer has very close ties with a political group based in Thailand's three southernmost provinces," he said.
The vehicle used as the bomb weapon is a four-door Mazda pickup that Abdulraza Dumidae reported as being stolen on March 31. This man is a driver of Tambon La-ae Administrative Organisation, which is based in Yala's Yaha district.
Abdulraza, now in military custody, is believed to have key information that could lead to the arrests of those behind the vehicle-bomb blast. "He has made a partial confession, and some pieces of information are useful," Yala's police chief, Maj-General Tanongsak Wangsupa, said.
Abdulraza was at the Wang Phraya Military Base in Yala's Raman district as of press time.
Surat Thani's military chief Maj-General Kuakool Innachak, meanwhile, said five security guards of the Central Festival Samui shopping mall were also detained at another military camp. "They are cooperative. They have answered all questions," he said, "We find one of them has inside information".
Kuakool said the military planned to hand them over to police after the seven-day detention period ended.
The vehicle bomb exploded at the Central Festival Samui late on April 10, injuring many victims.
While many people had suggested that the incident was politically motivated, Kuakool said the ongoing investigation focused on three possible motives: personal/business conflict, political conflict, and another operation to fan unrest in Thailand's deep South.
"So far, we can't find any link to the unrest at this point. It's just that the bombers may have lived in the southernmost provinces," Kuakool said.
He also said available evidence also did not find any link between the bomb blast and the fire at a local cooperative in Surat Thani, which happened on the same day.
A source said that forensic officials had collected a big box of evidence form the fire scene. "With the results from evidence examination and forensic tests, police should be able to conclude the cause of the fire within 15 days," it added.
Surat Thani Governor Chatpong Chatraphuti said security agencies were now stepping up security at key attractions of Koh Samui in the wake of the recent bomb blast.
He also disclosed that a special-task team would be closely monitoring Muslim residents in Koh Samui district too.