By The Nation
Officers of various precincts are studying security camera recordings and interviewing people seen with suspects, including taxi drivers.
There have been four arrests so far and warrants are expected to be sought for seven more suspects.
Investigators are in total probing nine bombs – six that exploded and three that were safely disposed of – and six arson attacks in six different locations.
A timeline compiled by The Nation based on information from police sources begins at 3.40pm on Thursday (August 1), when two bomb-like objects were noticed in front of Royal Thai Police HQ.
Police initially characterised them as fake bombs – containing full detonating equipment but no explosive material.
It was later announced, however, that they were homemade bombs set to detonate between 8 and 9am on Friday.
At 4.37am on Friday, Pathumwan police were alerted to fires at two department stores at the Samyan and Pathumwan intersections. Mall security and automatic extinguishers doused the flames and no one was hurt.
At 4.40, Phayathai police got a call about a fire at the single-storey Sidewalk Market on Soi Phetchaburi 19 in Ratchathewi district, behind the Indra Regent Hotel. The blaze destroyed 60 clothing stalls.
Officers from the Scientific Crime Detection Division found what were believed to be elements of fire bombs at the three fire locations, including timer circuit-boards attached to power banks and traces of alcohol.
The fire bombs were similar to those used to cause disturbances in seven provinces in the upper South in 2016. In Bangkok, the first was set to detonate at the DD House Building half an hour before the other two.
Security cameras at the malls recorded a man “planting” an object in the approximate right location at one mall, but no one was seen at the other.
At 6.10am, a bomb exploded at the entrance to Building B at the Government Complex in Bangkok’s northern Chaeng Watthana district. No one was injured.
Between 8.30 and 8.40, two more bombs exploded, one in front of the King Power Mahanakhon Building, injuring a security officer, the other in a carpark in front of the same downtown building, injuring an electrical technician.
At 8.40, a bomb detonated in front of the Office of the Permanent Secretary for Defence in Nonthaburi’s Pakkret district. Again, no one was hurt.
At 8.45, a second bomb exploded at Government Complex Building B, this time at the exit.
At 9.10 there was an explosion in front of Supreme Command headquarters. No one was injured.
At 11, a bomb disposal unit dismantled a second device in the same locale.