Thai police have released an image of the foreign suspect they arrested for allegedly playing a 'key role' in the country's deadliest ever bomb attack.

Thailand's prime minister said the man, who was seen wearing a baseball cap and sunglasses today, was the main suspect in the August 17 bombing.

Police would not say if he was the same suspect caught leaving a bag at the site of the blast on CCTV, but said he was involved in a second, smaller explosion the next day.

He was arrested in Sa Kaeo province, on the border with Cambodia, and has been taken to Bangkok for questioning. The police have issued arrest warrants for three more foreign male suspects.

The blast at a Hindu shrine in Bangkok killed 20 - including 17 foreigners - and injured more than 100.

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Detained: Thai police have released an image of the foreign suspect they arrested for playing a 'key role' in the August 17 bomb attack in Bangkok

Evidence: Royal Thai Army soldiers display the items seized from the Erawan Shrine bombing suspect after they arrested him in Sa Kaeo district

Chief suspect: Royal Thai Police released a sketch of the suspect (left) and a CCTV image of the main suspect (right) in the deadly shrine bombing in Bangkok

Explosion: The blast (pictured) at the Erawan Shrine in the commercial Rajaprasong district killed 20 and injured over 100

Television footage of the suspect showed a thin man with a short moustache who wore a baseball cap and sunglasses.

Officers issued two new arrest warrants and released images of a Thai woman and a foreign man yesterday after finding a remote-controlled car 'detonator' in an apartment raid.

It is unclear whether the man in his 40s, whose nationality is unknown, is the same man who was arrested today.

The apartment in Min Buri district was rented by a Thai woman identified as Wanna Suansun, 26, police spokesman Prawut Thawornsiri said.

He added that the police found 'bomb-making materials' such as gunpowder, 'fertiliser which can be used as explosive powder when mixed with other substances' and a remote-controlled car whose controller 'can be used as a detonator'.

They also found nuts and bolts, small light bulbs and digital watches, among other small objects.

Destruction: Thai soldiers inspect the scene after a bomb exploded outside a religious shrine in central Bangkok late on August 17

Wanted: Thai police issued two new arrest warrants and released images of a Thai woman (left) and a foreign man of unknown nationality (right) as part of the widening investigation

Explosive: Thai investigators are hunting two new suspects after finding a remote-controlled car 'detonator' (pictured) during an apartment raid

New leads: Thai police have issued arrest warrants for three more foreign male suspects (pictured, sketches of all three)

Police released a sketch of the man - who has short brown hair and light facial hair - who is believed to have lived in the apartment.

The arrest came after security forces arrested a first foreign suspect in weekend raids on the outskirts of Bangkok, in which they also found explosives.

Police found ten fake passports and bomb-making materials in the house on Saturday.

The man's passport suggested he was a Turkish national called Adem Karadag but the police believe the document is fake and his real identity is still unknown.

National police spokesman Prawut Thavornsiri said that the suspect looked like 'the one we are looking for', and he has since been charged with possessing illegal explosives.

Police confirmed he was not the suspected bomber in the wanted poster - rather someone who was part of the bomber's close network.

Yesterday, it emerged the police handed a £55,000 for information leading to the arrest of suspects to themselves - after bosses said staff had 'done their job'.

Police found ten fake passports and bomb-making materials in the house of another arrested suspect, Adem Karadag (pictured), on Saturday

Job well done: Police handed a £55,000 for information leading to the arrest of suspects to themselves - after bosses said staff had 'done their job'

Thai police have come under criticism for their handling of the investigation and 22 officers have been transferred from their posts for negligence.

Six of the 22 were immigration officers from Sa Kaeo, while the others worked in the Bangkok districts where the security forces conducted the weekend raids.

Police chief Somyot Pumpanmuang said he transferred the immigration officers because foreigners had been able to enter Thailand illegally in Sa Kaeo.

He said: 'That was my decision. I think that when a foreigner is able to illegally enter Thailand without proper scrutiny... I think those officers should be transferred.'

Speculation has centred on sympathisers of Uighur Muslims, opponents of the government, southern ethnic Malay rebels and foreign extremists.