The government said the attack during Monday's evening rush hour in Bangkok's commercial hub was aimed at destroying the economy. No one has claimed responsibility.
Jangling nerves in the capital on Tuesday, a small explosive device was thrown from a bridge towards a river pier, sending a plume of water into the air, but no one was injured.
Major-General Werachon Sukhondhapatipak said there were similarities between Monday's deadly blast and the smaller, Tuesday explosion, but added the authorities had not established links between the two. "Both were TNT bombs," he told Reuters. "There's a pattern, but we have not yet found links."
The man suspected of Monday's bombing at the Erawan shrine was seen in grainy CCTV footage entering the compound wearing a backpack, sitting down against a railing and then slipping out of the bag's straps.
Wearing a yellow shirt and with shaggy, dark hair, the young man then stands up and walks out holding a blue plastic bag and what appears to be a mobile phone. The backpack was left by the fence as tourists milled about.
National police chief Somyot Pumpanmuang said the suspect could be Thai or foreign.
"That man was carrying a backpack and walked past the scene at the time of the incident. But we need to look at the before and after CCTV footage to see if there is a link," Somyot told a news conference.
Police earlier said they had not ruled out any group, including elements opposed to the military government, for the bombing at the shrine, although officials said the attack did not match the tactics of Muslim insurgents in the south.
Prime Minister Prayuth Chan-ocha also referred to the man as a suspect without giving details. He said there were "still anti-government groups out there." He did not elaborate.
Junta spokesman Werachon dismissed rumors that the man was disguised. "There was no disguise. He was wearing a t-shirt and shorts," he said.
SEARCH FOR CLUES
Police were at the blood-splattered site on Tuesday, some wearing white gloves and carrying plastic bags, searching for clues to an attack that could hurt Thailand's important tourism industry and dent investor confidence.
Police said the death toll was 22, with 123 people wounded.