Devices made the same way as in South
The police team investigating the New Year bombings in Bangkok and Nonthaburi has concluded that a southern separatist group was responsible for the nine explosions. Police are now hunting for a man with a southern Thai accent who bought 300 silicon controlled rectifier (SCR) diodes, used in the assembly of bomb circuits, in Bangkok's Ban Mo area.
A highly-placed source in the investigation team said the insurgent group responsible for the nine bombs wanted to show its capability to launch terrorist attacks outside its home region.
Evidence collected from attack scenes and the detonation circuitry used to assemble the bombs supported the investigators' conclusion, the source said.
''After examining evidence thoroughly, it was found that the bomb detonation circuits are the same [as the circuits used by a southern insurgent group].
Moreover, the materials used to make the bombs are all the same,'' the source said.
The investigation team is now focusing its investigation on one insurgent group.
The materials used to assemble the nine bombs included metal boxes containing ball bearings and nails, a Casio 200 watch, a nine-volt battery and a small deodorant spray bottle containing gunpowder.
The same materials are used by the southern insurgent group, said the source.
The brand and model of diodes used in the bomb circuits was also the same as the devices the group used to launch attacks in the deep South. They are SCR diodes made by Motorola.
The owner of an electronics shop in Ban Mo told investigators that on Dec 23, one week before the bombings, he sold 300 of the SCR diodes of the same model, together with 300 nine-volt battery terminals of the same type that police collected from the bomb scenes, the source said.
The shop owner said the man who bought them wore a hat and spoke Thai with a southern accent.
Bomb disposal experts told the investigation team that the bombs used in the New Year attacks and terrorist attacks in the deep South were probably assembled by the same person.
Each bomb-maker has his or her own signatory bomb-making style, the source said.
The investigation team will report its findings to the Council for National Security (CNS) soon.
The CNS earlier believed that an ''old political power clique'' was responsible for the Bangkok bombing.
''Now it's rather clear that it was a southern insurgent group that launched the attacks,'' the source said.
Assistant national police chief Pol Lt-Gen Phanuphong Singhara na Ayutthaya, who leads the bomb probe, has ordered the investigation team to gather information to identify insurgent groups capable of launching such an attack, another police source said.
Another investigation team, led by assistant police chief Pol Lt-Gen Jongrak Juthanont, has asked the Criminal Court to issue arrest warrants for two suspected New Year bombers who appear in video footage from two security cameras, one at the Saphan Khwai intersection and another at Major Cineplex Ratchayothin.
The team will make public the footage of the suspect at Major Cineplex on Wednesday, to seek more information from the public.
The team has already publicised footage of the male suspect at the Saphan Khwai intersection and received more than 300 tips from the public.