The Criminal Court approved Bang Na police's request for the first detention of the four suspects allegedly involved in the bomb attack on late Tuesday night as the investigation is in progress.
The suspects were identified as Anusorn Phinitkhun, 45, Suna Thinkaew, 53, Khamprai Sangsawaeng, 45 and Ms Chanapha Denmat, 35.
The four were allegedly in a pickup truck and hurled a bomb into Mr Abhisit's residence in Soi Sukhumvit 31 at around 11.30pm.
The explosion damaged the roof and shattered windows but no one was injured.
Bang Na police manning a checkpoint near the Meteorological Department on Sukhumvit Road found the suspects' pickup truck with the four suspects.
After searching the vehicle, police found four M-26 grenades, a 9mm gun and bullets. The four will be charged for possessing firearms and ammunition without licences and carried firearms without permission.
The four suspects denied all charges.
Police said 12 more witnesses would be questioned pending forensic results and the suspects' criminal record examination. The court then approved the police request to detain the suspects for 12 days from today until Jan 27.
The police also objected a bail attempt, saying the case was considered serious offences and the suspects could flee.
Meanwhile, small improvised explosive devices were thrown into the barricade of the protest site near Nang Lerng horse racing course occupied by the Network of Students and People for Reform of Thailand (NSPRT), the alliance group of the People's Democratic Reform Committee (PDRC).
The two explosions occurred at around 12.45pm and 12.50pm.
Volunteer guards rushed to inspect the area around the protest site and inside the horse racing course premise before detaining a suspect with a fishing gun.
The suspect was identified as Sampan Rueangsi, 41. He claimed that he was a temporary worker for the race course and had nothing to do with the explosions.
Mr Sampan would be handed over to police for further investigation.