BANGKOK — Nearly a month after the deadliest bombing in recent Thai history, Thailand’s national police chief made his most explicit comments on Tuesday about who carried out the attack here and why.

The perpetrators, he said, were linked to Uighur militants, radical members of an aggrieved ethnic minority in western China, who struck to avenge Thailand’s forced repatriation of Uighurs to China and Thailand’s dismantling of a human smuggling ring.

If true, the bombing — which killed 20 people, most of them ethnic Chinese tourists — would be the first known Uighur terrorist attack outside China, a development that could have security implications for China and its citizens worldwide.

But many questions remain unanswered about the attack, for which no one has claimed responsibility.

Suspicion fell on Uighur militants almost immediately after the bombing, which occurred just weeks after Thailand sent 109 Uighurs back to China, their heads covered in hoods, a move widely criticized by foreign governments and activists who said the Uighurs were likely to face persecution there.