The potential suspects are believed to be part of the operation team that carried out the attacks on Aug 2, according to the source.
Currently, nine people are being detained for alleged involvement in the blasts and arson attacks that injured five people.
The detained include two men from Narathiwat who were arrested on suspicion of planting bombs in front of the police headquarters on Aug 1.
The three latest suspects are believed to have planned the Aug 2 bomb attacks from a neighbouring country, before entering Thailand to take part in the operation and then fleeing back over the border.
Deputy Prime Minister Prawit Wongsuwon yesterday (Aug 14) told media that police and related authorities have contacted officials in the neighbouring country to seek the suspects’ extradition. Gen Prawit refused to reveal the name of the country.
In a related development, Pol Col Phopthorn Jitman, deputy chief of Metropolitan Police Division 6, said police today will ask the Southern Bangkok Criminal Court to grant the extended detention of the first two suspects.
Lu-ai Saengae, 22, and Wildon Maha, 29, both from Rueso district in Narathiwat, were apprehended on an inter-provincial bus at a police checkpoint in Chumphon province on Aug 2, on suspicion they planted the devices in front of Royal Thai Police headquarters in Bangkok a day before the blasts.
The pair were charged with criminal conspiracy, illegal possession of explosives, attempted murder, and illegally carrying firearms. The explosives were set to go off at 8am on Aug 2, but were defused by bomb disposal officers.
Mr Lu-ai is being detained at Pathumwan police station while Mr Wildon is being held at Bang Rak police station.
However, Col Phopthorn declined to comment on reports that investigations into the bomb blasts would be transferred to the Crime Suppression Division (CSD).
However, a source at the CSD told the Bangkok Post that the CSD was preparing to take over the case.
National Police Chief Chakthip Chaijinda is now expected to forward the case to the CSD to streamline the investigation.
Read original story here.