BANGKOK

Thai police have shifted the focus of their investigation into a bombing at a Bangkok shrine that killed 20 people, saying Monday that the blast was partially inspired by domestic politics.

The claim comes two weeks after police first linked it to the deportation -- and subsequent international outcry -- of 109 Uighur Muslims from a Thai holding center to China.

​Police Chief Somyot Poompanmoung told reporters that one of the 17 suspects -- "Aod Payungwong or Yongyuth Pobkaew" -- was known to have been involved in a domestic political bombing last year.

"Because of Aod's involvement in the case, we cannot rule out domestic terrorism as one of the motivating reasons for the bombs," he said.

The police chief said that among many other cases, Payungwong was arrested in 2010 in connection with a blast at an apartment building, and in 2014 a warrant was issued for him in connection with an explosion in a Bangkok district.

Both were carried out during anti-government street protests in Bangkok.

“A motive [of the Bangkok shrine bombing] was the authorities’ crackdown on a Uighur human trafficking racket," Poompanmoung said. "Investigators believe that there are people who hired the perpetrators. Different groups of people were involved and they shared the same objective and desire."

“We can’t rule out political motives” because Payungwong was also involved, he underlined.

Police Gen. Chaiyapol Chatchaidech told reporters that the bombing was carried out by two teams of people working together. 

"There are 17 suspects total, working out of two apartments with two Thai nationals involved," he said. 

On Monday, the Bangkok Post reported that police had asked that the passport of another Thai suspect -- Wanna Suansan -- be revoked as she had failed to answer a police summons. 

The 25-year-old's family lives in southern Phangnga province, where the majority of the rural population is Muslim.

Her husband is reported to be a Turkish national and she initially told her family that she is now in Kayseri, in central Turkey, but offered no proof.

The police chief underlined Monday that the primary motivation for the bombing was still thought to be a crackdown on trafficking by the government earlier this year that disrupted a network used to ferry Uighur from China to Turkey via Thailand.

The Uighur are a Muslim Turkic minority from northwestern China who claim their cultural and religious rights are curtailed by the Chinese authorities. Thousands have fled with the aid of people smugglers, some to settle in Turkey.

Poompanmoung added that the two Uighur suspects in custody -- Adem Karadag and Yusufu Meraili -- had confessed to the bombing after being presented with "insurmountable evidence”.

“We’d gathered so much evidence that the suspects could no longer deny their involvement and had to admit that they were involved,” he said, adding that Meraili had also confessed to Payungwong's involvement, stating that the Thai man had provided him with the materials to make the explosive device used in the bombing.

Poompanmoung underlined that police did not coerce either man into a confession -- an act that Thai police have frequently been accused of.

On Monday, Karadag's lawyer Choochart Khanphai -- who refers to his client as Bilal Muhammed -- attended the army base with an Anadolu Agency correspondent where Muhammed is being held, only for both men to be told that the case is to be moved from a civilian court to a military court and the lawyer would need to refile paperwork in order to see his client. 

Khanphai -- who said he had not been able to see Muhammed since last Wednesday, which was prior to the "alleged" confession -- later told Anadolu Agency that he has now been given permission by the military court to see his client in a couple of days time.

On Friday, he claimed that the allegations “did not add up”, noting that his client had been interrogated through the night last week -- just one day after being hospitalized -- and he was not even in the country at the time of the bombing.

“My client has said he arrived in Thailand on August 21, days after the bombing,” he told Anadolu Agency. "Muhammed was passing though Thailand to Malaysia, where he was looking for a job. Muhammed knows nothing whatsoever about the bombing."

Despite being found in possession of a fake Turkish passport bearing his image and the name Adem Karadag, Khanphai says his client is in fact Turkish, and had been living in Istanbul for the past decade.

The lawyer has said that Muhammed has claimed that he, his elder brother and younger sister have Turkish nationality, but as an immigrant he was not allowed to officially leave the country until he had lived there for 20 years.

He said the family worked in the "truck driving business" and didn't make very much money.

An unnamed source at the Turkish immigration department -- who did not wish to be named as he was not authorized to speak to media -- told Anadolu Agency on Monday that Uighur arriving from overseas are given humanitarian residency and -- "under normal procedure" -- can then be granted a passport on obtaining citizenship after just five years.

They can then come and go as they please, he underlined.

Poompanmoung said Monday that police were now working with the Turkish embassy in Bangkok to determine Muhammed's nationality. 

The Aug. 17 Bangkok bombing left 20 people dead and over 100 injured.

The deportation to China of 109 Uighur in July saw families separated, husbands taken away from wives and fathers and mothers from children.

As a chorus of protests by international organizations and foreign governments against Thailand’s decision to send the group to Beijing grew, a further group of eight women and children were also sent to Turkey.

The reaction to the deportation was particularly strong in Turkey, where a group of pro-Uighur people vandalized the Thai consulate in Istanbul on July 9.

*Anadolu Agency correspondent Satuk Bugra Kutlugun contributed to this story from Ankara.