After the man admitted he was the suspect seen in video in a yellow shirt, he confessed to the bombing, Thailand national police spokesman Prawut Thavornsiri told reporters.
Police used new surveillance images to confirm they had the man responsible for the bombing, the spokesman said. The images showed the suspect walking into a restroom and changing his clothes before he walked out.
"He did admit that the man in the photo was him, and each of his admissions they became all connected. And finally he admitted it all," Prawut said.
Police said they are confident that the man -- who goes by several names including Adem Karadak -- carried out the bombings that also injured more than 100 people.
Police on Saturday will take Karadak and Yusufu Meirailee -- who was arrested earlier this month -- to the crime scene at the Erawan Shrine. The duo will go to Hua Lumphong train station where they allegedly met to swap the bomb rucksack. They also will visit the spot where they allegedly dropped a mobile phone used to set off the bomb, authorities said.
CNN reached out to an attorney for Karadak but didn't hear immediately back.
Also Friday a Thai military court issued arrest warrants for 17 people, three of whom were named publicly for the first time as members of the network responsible for the bombing at the shrine.
Two of the suspects -- Ali Noor and Manu Muhammad Ismail -- are suspected of buying SIM cards that were used in triggering the bomb.
Another man is believed to be the suspect who dropped a second bomb at a pier. That explosive fell into the water and didn't injure anyone.
They will face charges of premeditated murder and jointly making bombs that resulted in deaths, injuries and losses of property. If convicted, they could face the death penalty, Prawut said.
The shrine, at a bustling intersection near a large shopping mall, is a big draw for tourists. At least seven people from other Asian countries were reported to be among the dead as well as one Briton. The site is popular among Buddhists as well as Hindu and Sikh members of Thailand's Indian community.