They released a sketch of the person they believe carried out Monday’s bombing, based on CCTV images of a man dressed in a yellow T-shirt who was seen leaving a backpack at the shrine where the attack took place.
An arrest warrant has been issued for the man, who is seen in the CCTV footage above. Two other men in the footage – one wearing red, the other white – are also being treated as suspects.
Thai police chief Somyot Poompanmoung said: “I believe that this act was not carried out alone. It was probably carried out by multiple individuals with the support of a network. It’s done by someone who knows the escape route. This type of act cannot be done alone.”
He said the man in the CCTV images could have been disguised, but that people who looked similar would be called in for questioning.
His nationality has not been established. although the police suspect he is a foreigner because of his fair skin. They are also convinced Thais were involved.
The Thai government believes the bombing, which claimed the life of British law student Vivian Chan, was carried out to damage the economy, which relies on tourism. Of the 20 people who died, more than half were from other Asian countries, while 120 were injured.
Following the attack at the Hindu shrine, on Tuesday a bomb was thrown from a Bangkok bridge and exploded in a river. No-one was hurt. Although both bombs used TNT, a direct connection between them has not been established.
Most of the victims of the shrine bombings had wounds inflicted by ball bearings packed in the bomb. Two non-Thais have been interviewed in connection with the blast.
Police maintain an open mind about the motivation of the bombers, amid speculation they could be opponents of the military government or ethnic Muslim Uighurs.
They say the tactics used are not the same as those employed by Muslim separatists in the south of the country or so-called “red shirt” supporters of the previous administration.
Angel Rabasa, an expert on Islamist militancy at the Rand Corporation, said said the attack could have been carried out by Islamic State or another Islamist group.