Thai authorities unveiled the restored centrepiece of the Erawan Shrine, in the latest bid to restore confidence in Bangkok 18 days after a bombing that left 20 dead.

In the past week, police have arrested two people and identified seven more believed to be part of a network that carried out the August 17 blast, which also injured more than 120 people.

They have intentionally avoided calling it an act of terrorism for fear of hurting Thailand's image.

"The most important issue for the country's image is to restore confidence about safety," minister of culture Vira Rojpojchanarat told reporters at the ceremony,.

He said the event was intended to "create confidence and raise the morale of (Thai) people and tourists".

The ministry's fine arts department repaired 12 areas of the shrine's gleaming golden statue of the Hindu god Brahma that were damaged by the attack, notably on its four-headed face where a chin was blasted out.

"Every day the police and national security are making progress on the case," he said.

In the past week, the investigation picked up pace with police arresting the two suspects and carrying out two raids on homes in Bangkok where bomb-making materials were discovered.

At a third raid on Thursday, authorities found "suspicious fluid in a barrel" that was being analysed by explosives experts, said national police spokesman Prawut Thavornsiri.

Thai authorities have suggested that at least two of nine suspects are possibly Turkish.

That prompted the Turkish Embassy in Bangkok to say it has not received confirmation from Thai authorities about the nationalities of the suspects.

The Turkish connection has boosted a theory that the suspects may be part of a group seeking to avenge Thailand's forced repatriation of more than 100 ethnic Uighurs to China in July.

Thailand is believed to be a transit stop for Chinese Uighurs attempting to go to Turkey.

Uighurs are related to Turks, and Turkey is home to a large Uighur community.

The Erawan Shrine is especially popular with Chinese tourists, feeding the speculation that it could have been targeted by people who believe the Uighurs are oppressed by China's government.

China has alleged that the repatriated Uighurs included some who intended to join Islamic State fighters in Syria.

In another finding that could support a link to Uighurs, police said a man arrested on Tuesday who is considered a main suspect in the bombing was carrying a Chinese passport.

The passport indicated he was from the western Chinese region of Xinjiang, but Thai authorities had not yet verified its authenticity, Mr Prawut said.

Xinjiang is the home of the Turkish-speaking Uighurs.

Authorities on Thursday identified the suspect but issued two different spellings of his name - Mieraili Yusufu and Yusufu Meerailee - and said he faces charges of possessing unauthorised explosives.

Police said they found his fingerprints on a bottle of bomb-making material recovered from a flat that was raided over the weekend.

The other suspects include a Thai woman identified as Wanna Suansan and said to be married to a Turkish man. Both are being sought by Thai police.