A key suspect in last month's deadly Bangkok blast handed the backpack bomb over to a man in a yellow T-shirt later seen placing it at a busy shrine, Thai police say.
Mystery surrounds the motive of the alleged network behind the August 17 bombing that left 20 people dead in the heart of Bangkok and rocked Thailand's key tourist industry.
But after appearing flat-footed in response to the unprecedented attack on Thailand, police have trumpeted the arrest of two foreigners and say they have identified several other suspects.
One of the two men in custody, Yusufu Mieraili, was arrested last week near the border with Cambodia and has since been quizzed by military and police investigators.
Mieraili, 25, who was detained in possession of a Chinese passport, has confessed to playing a central role in the operation, according to police.
On Wednesday (local time) he was taken on a second re-enactment of his alleged role in the crime – a standard police procedure.
"This is the area where he met the man in a yellow shirt to exchange the backpack," national police spokesman Prawut Thavornsiri told reporters outside a Bangkok railway station.
Mieraili, whose hands were bound while he wore a bulletproof vest during the re-enactment, handed a "heavy backpack" to the bomber outside the station, Prawut said.
That man was seen on security footage apparently placing the same bag at the shrine and calmly walking off moments before the blast.
Police have not revealed Mieraili's nationality, although the birthplace on the passport he was found with is listed as Xinjiang – home to China's Muslim Uighur minority and often hit by unrest.
Speculation has hardened on links to China's Turkic-speaking Uighur minority, many of whom complain of religious and cultural discrimination.
Thailand deported scores of Uighurs to China early in the summer, prompting protests in Turkey where some nationalists hold a deep affinity with the minority group.