Three suspects -- a Pakistani man and two Malaysians -- were detained a few days ago, Malaysia's Inspector-General of Police Khalid Abu Bakar told a briefing.
"We are assisting Thai police regarding this probe. We feel these three can assist us in the investigation," he was quoted as saying by the Star. Khalid, however, said the suspects would not be handed over to Thai police just yet.
"We feel there is no need at present to hand them over to the Thai authorities. We are working together with our Thai counterparts. Let us investigate the matter first," he said.
Thai authorities have arrested two suspects in connection with the twin bombings last month. One of them, Mieraili Yusufu, identified the alleged mastermind as Abdulrahman, also known by the alias Izan.
Izan left Thailand on a Bangladesh-bound flight on August 16, a day before the bombing.
Thai police had also sought help from Bangladesh through Interpol to help locate the mastermind behind the country's deadliest bombing at the Erawan Brahma Shrine after investigations indicated that the Chinese man may have fled there.
Mystery still surrounds the motive of the group accused of being behind the August 17 bombing that left 20 people dead in the heart of Bangkok.