Thai police have arrested a man they said was "likely involved" with the bombing of a Bangkok shrine that left 20 people dead and scores injured.

Key points: "Turkish national" arrested over Bangkok bombing

"Turkish national" arrested over Bangkok bombing "Not yet clear" if man arrested is CCTV suspect

"Not yet clear" if man arrested is CCTV suspect Passports, bomb-making materials found in apartment

Passports, bomb-making materials found in apartment Thai police not ready to exclude any possibility about who was behind the attack

The 28-year-old man is a "Turkish national", according to Internal Security Operations Command (ISOC) spokesman Colonel Banphot Phunphien.

"He carries many passports. It's unusual how he carries so many passports," Colonel Banphot said.

It is the first arrest in connection with the bombing that tore through the crowded Erawan Shrine on August 17, which killed mostly Asian tourists in Thailand's worst single mass-casualty attack.

Police and military seized the man during a raid at a flat in Nong Chok district, in the eastern outskirts of Bangkok, on Saturday morning.

"We have found components of bomb-making materials in his apartment and I am confident that he is likely involved with the bomb attack," deputy national police chief General Chaktip Chaijinda told reporters in a live televised broadcast.

The man had been in Thailand since January 2014 and was being held at a military facility on initial charges of possessing illegal explosives, police said.

"It's unlikely to be terrorism. It's not an international terrorist act," police chief Somyot Pumpanmuang told a news conference.

"He is a foreigner, but it's unlikely that he is an international terrorist, it's a personal feud."

He did not explain how police had come to that conclusion, but said the motive was "taking personal revenge for his comrades".

"He got angry on behalf of his friends and family members," Somyot added, without elaborating further.

Thai Royal Police officials remove evidence from the flat where the suspect was arrested. ( Reuters )

Police had been searching for a prime suspect, described as a foreign man, who was captured wearing a yellow t-shirt on security cameras leaving a bag at the shrine moments before the blast.

General Chaktip said it was "not yet clear" whether the man now detained was the same as the one in those images.

Police have been in a war of words with the city government, known as the Bangkok Metropolitan Administration, over broken security cameras, saying a lack of maintenance has hindered their investigation.

Attack aimed at damaging tourism: investigators

The majority of those killed were ethnic Chinese worshippers from across Asia, who flocked to the shrine in the belief that prayers there brought good fortune.

CCTV footage showed a suspect entering the shrine with a backpack (left) and then leaving without it (right). ( Supplied: Twitter )

Investigators have said the attack was clearly aimed at damaging the tourism industry but insisted Chinese tourists, who visit Thailand in larger numbers than any other nationality, were not singled out.

Earlier this week Thai police said they were not ready to exclude any possibility about who was behind the attack.

Potential perpetrators named by the police and experts have included international jihadists, members of Thailand's southern Malay-Muslim insurgency, militants on both sides of Thailand's festering political divide or even someone with a personal grudge.

Some security analysts have also speculated China's ethnic Uighur minority or their co-religious sympathisers may have been behind the attack, motivated by Thailand's forced repatriation of more than 100 Uighur refugees last month to an uncertain fate in China.

Police said three Uighur Muslims, among dozens detained in the kingdom for illegal entry last year, have been questioned over the bombing.

AFP