The Criminal Court approved an arrest warrant on Wednesday for the man believed to have placed a bomb at the Erawan Shrine, police spokesman Prawut Thawornsiri said.
Pol Lt Gen Prawut said the warrant was endorsed by the South Criminal Court following a request by the Royal Thai Police.
Pol Lt Col Somkiat Ploythupthim, an investigator at Lumphini police station, said the warrant was issued for a foreigner based on an identikit sketch of him composed from images captured by CCTV.The man faces bombing and murder charges, he added.
Pol Lt Gen Prawut said there could be accomplices to the carnage on Monday night that killed 20 people and injured 125 others. At least one of them could have occupied the bench inside the shrine for the suspect before he arrived. Another could have shown him where to place the bomb, he added.
The sketch of the man was released by the Royal Thai Police on Wednesday. He was seen wearing dark framed glasses, a yellow t-shirt, baggy shorts and sweat bands on his wrists and forearms shortly before the bomb went off.
Police are offering a 1 million baht reward for information leading to his arrest.
Pol Lt Gen Prawut said he hoped the suspect was still in the country as immigration authorities have been on full alert at all airports and border checkpoints and now have the sketch to help them.
Prime Minister Prayut Chan-o-cha said Thailand needed no outside help to shed light on the bomb and was confident in the investigative powers of the police to solve the crime.
The prime minister earlier warned the bombers to turn themselves in for their own safety.
Police chief Somyot Poompunmuang said the bombings were intended to discredit the government and a group of people was behind them.
"The motive is to discredit the government and make it unacceptable to other countries when it comes to safety in the country," Pol Gen Somyot said.
