An arrest warrant has been issued for a foreigner believed responsible for Monday's fatal bombing at a Bangkok shrine, as Thailand's ruling junta said the attack was unlikely to be "international terrorism."
Thailand's police chief said on Thursday that at least 10 people were suspected of involvement in the bombing at the Erawan shrine that killed 20 people, more than half of them foreign tourists.
"It is a big network. There was preparation using many people," police chief Somyot Poompanmuang told reporters.
"This includes those who looked out on the streets, prepared the bomb and those at the site and ... those who knew the escape route," he said.
"There must have been at least 10 people involved."
On Wednesday police released a sketch of the subject of the warrant - a man spotted on closed-circuit television footage examined after the blast.
Police said on Wednesday that man wasn't likely to be Thai based on the sketch done from the video surveillance images, but added that he may have been wearing a disguise to conceal his identity, the Bangkok Post reported.
The security video footage shows a man wearing a yellow t-shirt and baggy shorts leaving a black backpack at the shrine 15 minutes before the explosion on Monday. Two other men standing nearby have also been identified as suspects.
Assistant national police chief Prawut Thavornsiri told reporters on Wednesday that he hoped the suspect was still in the country and offered a $28,000 reward for information leading to his arrest.
On Thursday,the ruling military junta said the attack was not specifically aimed at Chinese tourists, although Chinese were the largest group among the foreigners killed in the blast.
"Security agencies have cooperated with agencies from allied countries and have come to the preliminary conclusion that the incident is unlikely to be linked to international terrorism," said Colonel Winthai Suvaree, a spokesman for the junta, known as the National Council for Peace and Order.
Speculation has been mounting as to the possible motive behind the deadly blast.
Initial assumptions that the suspect was of Uighur origin were dismissed by Prime Minister Prayut Chan-o-cha on Wednesday. The Uighurs are a Muslim ethnic minority group from western China who aspire for autonomy from the mainland.
Citing police sources, the Bangkok Post said on Wednesday that Uighur militants may have planted the bomb in retaliation to Thailand's deportation of 109 Uighur refugees to China.
Others say the bomb blast may be related to an upcoming vote on a draft constitution aimed at bringing back democratic rule.
The National Reform Council (NRC), an advisory group set up by the ruling military junta, is set to vote on September 7. If the vote passes, the draft charter will be put to a referendum that could take place in January 2016.
"Thailand is locked in a doom-loop, with a junta that is moving towards a form of constitution and return to electoral politics but this is totally rejected by the opposition," explained Steve Wilford, Asia Pacific Director for Global Risk Analysis at security consultancy Control Risks Singapore.
The Democrat Party and fellow opposition group, the Pheu Thai Party, reject claims that the draft charter is democratic, saying it was designed to restrict the powers of elected leaders.
The draft contains a few controversial clauses such as protecting army generals who came to power in last year's coup and allowing unelected individuals to become prime minister.
Former Prime Minister Yingluck Shinawatra has also questioned the new charter.
"A democratic constitution must be connected to people, meaning it must allow the voice and decision of the majority of people to have an important role and not just let them choose some representatives pre-selected by certain groups of people," she wrote in a Facebook post on Monday.
Thailand has been in political paralysis since last year when a power struggle broke out between "Red Shirt" supporters of longtime rulers the Shinawatra family and "Yellow Shirt" royalists. The Yellow Shirts' support base includes former generals aligned with the opposition Democrat Party.
After months of violent protests between the two camps, a military junta seized power in May 2014 for the second time in a decade. Led by army chief and now Prime Minister Prayuth Chan-ocha, the military considers itself a neutral arbiter and restorer of peace.
"Militants loosely affiliated to the red shirt movement may have viewed criticisms of a draft constitution as sanctioning violence," Wilford said.
Indeed, speculation of a political motivation behind Monday's bombing is high, especially since experts appear to largely rule out the work of domestic terrorists.
"It's going to be difficult to convince people it's a terrorist attack from southern insurgents because those attacks are always concentrated in southern provinces," Suchit Bunbongkarn, director at Institute for Security and International Studies remarked on Tuesday.
Alongside the wrestle for power in the capital, Thailand has experienced a decade-long conflict over autonomy in the Muslim-dominated areas along the country's border with Malaysia.
Aim Sinpeng, lecturer in comparative politics at the University of Sydney, also pointed to the location of Monday's explosion as evidence of political plotting. The bomb blast took place on the same busy Ratchaprasong street intersection as 2010's bloody crackdown on red shirt supporters.
"The site of Monday's bomb blast exemplifies political struggle in Thailand," she noted. "Subsequent protests and upheavals occurred at that very intersection [since 2010] so we have to look at Monday's attack from a broader political perspective."
In a country that's gone through more than 20 prime ministers since 1946, Thai citizens are no stranger to political violence. Earlier this year, there was a grenade attack at a Bangkok courthouse and a bombing at a popular shopping mall. Police said the perpetrators of both incidents were from the same network.
- Reuters contributed to this report.