At least 123 more were injured by the powerful blast which hit a popular landmark heavily frequented by Thais and tourists alike at 6:55 pm.
One Filipino victim and two Chinese nationals were among those killed, outgoing police chief Somyot Pumphanmuang said. Twelve died at the scene and another seven have since died in hospital, according to the latest information from authorities.
"We have not discarded any possible motive," Somyot said at a news conference at the Royal Thai Police headquarters, located meters away from the scene of the attack. Despite media reports indicating one bomb was attached to a utility pole while a second detonated from a motorcycle, Somyot denied a car bomb was involved, saying the bomb was planted on the scene.
While no one has taken credit for the attack and authorities said it's too early to speculate, Defense Minister Prawit Wongsuwan told Reuters it was meant to harm Thailand's economy.
"The perpetrators intended to destroy the economy and tourism because the incident occurred in the heart of the tourism district," Prawit said.
Anusith Kunakorn of Thailand's National Security Council said "details about the explosion are still confusing, so we cannot conclude whether it is about an accident or a political incident. Related authorities are urgently working to clarify this matter. Once we have conclusive information, we will inform the people."
The bomb left a gruesome scene. Photos showed blood, bodies and human remains around the shrine as rescue workers rushed to provide aid near the shrine, which is a popular tourist destination.
Soon after the blast, police spokesman Prawuth announced bomb units were dispatched to the scene on suspicion there more bombs. Despite reports two more bombs were found and disarmed, Prawuth said they turned out to not be bombs.
In images tweeted by JS 100 radio just after the blast, fires were burning in Sukhumvit Road, which runs through the capital's cosmopolitan center.
Photos from the scene appeared to show an injured Caucasian woman being taken away on a stretcher.
There is no indication yet of what caused the explosion during rush hour. Roads around the area have been closed, and authorities said the area would remain closed Tuesday while the scene is investigated.
Surrounded by luxury malls and hotels, Rajaprasong intersection is in the heart of Bangkok's commercial shopping district. The Erawan Shrine is an important, sacred symbol in the Thai capital. In 2006, a mentally ill young man damaged the shrine with a hammer and was immediately killed by an angry crowd.
An area popular with the Bangkok elite, it was also the epicenter of protracted anti-government street protests in 2010.
Earlier this year a small bomb detonated not far from the scene of tonight's blast outside one of the capital's most popular shopping malls.
No one was injured in the 1 Feb. attack which occurred during the evening between the Siam Paragon shopping mall and BTS Skytrain station.
Authorities attributed that attack to political groups opposed to the military regime. Thailand has been under military rule since it seized power in May 2014.
In April a car bomb exploded in the basement of shopping mall on Koh Samui in southern Thailand, injuring seven people. The car used in the attack was reported stolen from a province the deep south, where security forces have been engaged in a long and bloody conflict with a homegrown insurgency movement seeking independence.
Despite widespread rumors online, the military government has not ordered businesses and schools closed tomorrow, according to junta spokesman Winthai Suwaree. The BTS Skytrain and MRT subway systems are expected to be operating as normal.
However late Monday night, the Bangkok Metropolitan Administration announced 438 schools in greater Bangkok will be closed.
The Thai International Red Cross Society announced it has adequate supplies of blood at this time.