Police will issue an identikit image of a man who allegedly drove the stolen pickup truck used in the Koh Samui car bomb.
The bronze Mazda pickup truck carrying the bomb exploded at a car park of the Central Festival mall on April 10.
Police spokesman Pol Lt Gen Prawut Thawornsiri said work on the identikit image was almost finished. Police had received information from a witness who confirmed he saw the man driving the stolen truck to the mall.
"If the witness says we have captured his likeness, we will seek approval from the court to issue an arrest warrant,'' he said.
Meanwhile, police have now detained two more suspects for questioning over the blast.
The first man, identified as Abdulroning Dueramae, 51, or "Bangyi", is the owner of a second-hand car retail business in Yala, Pol Lt Gen Prawut said.
Though he declined to identify the second suspect, security forces on Saturday searched a house in Patae neighbourhood of Yala's Yaha district and took the house's owner, Sabidi Sasaebing, 33, in for questioning.
Mr Sabidi, a teacher in Pattani's Yarang district, was held at the 41st special task force ranger unit.
"I believe the two suspects have knowledge about the incident, though they did not give useful accounts during initial interrogation," said Pol Lt Gen Prawut.
Four vehicles were found to have been used in the attack, and police are investigating, he said.
Meanwhile, an investigation team is on the lookout for a white Isuzu pickup believed to have taken the bombers from Koh Samui.
That pickup was resold by a second-hand car garage in Nonthaburi, owned by a man called Kai, to Bangyi's garage in Yala.
Mr Bangyi was reportedly taken to a military camp in the deep South for questioning.
Police received information that Mr Bangyi also bought the bronze Mazda pickup detonated in the blast from Kai.
Police believe the men behind the attack are key political figures in the South, with whom Mr Bangyi has worked as he was an election canvasser for former politicians in the area.
Meanwhile, police will further question Abdulasa Dumeeda, who told police that a group of seven or eight men stole the bronze Mazda used in the bomb attack, though he had previously driven it for the La-ae tambon administration organisation (TAO) in Yaha district on March 31.
Mr Abdulasa was taken to the Southern Border Provinces Police operation centre for questioning, where he was reportedly in a stressed state.
Two witnesses say they saw Mr Abdulasa getting off the pickup truck to speak to Mr Sabidi and another person shortly before he reported the truck stolen, according to investigators.
Mr Abdulasa may then have taken the vehicle to those who carried out the attack, they said.