Thailand’s former Prime Minister Yingluck Shinawatra talks to reporters before she leaves Bangkok’s Criminal Court, Thailand, in this Sept. 29, 2015 photo.

The son of ousted Thai premier Thaksin Shinawatra has handed police a reward of nearly $200,000 for their investigation into the deadly Bangkok blast, after authorities declared the first suspect arrested was the bomber.

The unprecedented August attack at a shrine in a bustling shopping district killed 20 people, mostly ethnic Chinese tourists, landing a fresh blow to the nation’s image as a holiday paradise after last year’s military coup and months of street protests which preceded it.

The reward from Panthongtae Shinawatra — the first born son of populist leader Thaksin — follows Thai police rewarding their own officers some $84,000 for arresting the bombing suspect two weeks after the blast.

“My team has handed seven million baht ($192,000) to the national police headquarters to boost the spirits of officials,” Panthongtae declared in a Facebook post on Saturday.

Thailand’s national police chief Jakthip Chaikinda confirmed the money had been received, telling reporters Sunday that the sum was marked for police officers involved the investigation and those who provided tip-offs.

It was not immediately clear if any members of the public would receive a cut for tip-offs. The earlier reward from police was earmarked only for officers as officials at the time said they had not received any public tip-offs after their call for information.

After weeks of an often confusing and contradictory probe, police last month announced that the foreign man they had arrested in possession of bomb-making equipment in August was the main yellow-shirted suspect seen on CCTV leaving a rucksack at a shrine moments before the blast.

They said the man — named by police both as Bilal Mohammed and Adem Karadag — had confessed to planting the bomb. The suspect’s lawyer later confirmed his client had admitted doing so.

But mystery still shrouds the motive for the unclaimed attack.

On Sunday Jakthip said police had not ruled out any motive for the crime with warrants out for more than a dozen other suspects believed to be involved.

There is only one other man in custody over the attack, a foreigner named as Yusuf Mieraili who is a Chinese passport-holder of Uighur ethnicity. Authorities have not confirmed the nationality of either of the two held.

Strong speculation has centered on a link to militants or supporters of the Uighurs, an ethnic group who say they face severe persecution in China.

But Thai authorities have avoided using the word Uighur largely, analysts say, for fear of angering China — one of the ruling junta’s few international friends.

In July the kingdom forcibly deported a group of 109 Uighurs back to China, sparking widespread condemnation.

Police have previously said they believe the bombing was a revenge attack by a people-smuggling gang angered at a recent crackdown on their illicit business.

And in a new twist last week they said domestic political grievances could also have been a factor in a country bitterly divided by rival factions, revealing one local suspect was linked to previous bombings in the kingdom.

Thailand’s long-running political schism roughly pits the rural and urban poor loyal to Thaksin, toppled in a 2006 coup, against royalist elites backed by large portions of the military.

Thaksin currently lives abroad in self-imposed exile after a corruption conviction that he insists was political. His sister, ex-premier Yingluck Shinawatra, was forced out of office days before the current junta seized power last May.

In his post Saturday Panthongtae criticized officials who had linked the blast to domestic politics when the evidence pointed to foreigners, saying they “should not receive a single baht” of the reward.

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