The man was identified as Samran Muangkhiew, or “Ake Lok Nueng”, who had been wanted under an arrest warrant since March 15.

He was found by police at the Thanyaburi Men Aid Centre, Pathum Thani province.

After a two-hour interrogation, Samran confessed that he dropped a cigarette on a bunch of leaves near garbage bins under the bridge after he went to the toilet. The cigarette caused the fire, he said.

The 31-year-old said he was scared so he ran away.

He said he was then rounded up by police as a homeless person and sent to the Thanyaburi Men Aid Centre on March 13.

Metropolitan Police chief Lt-General Sanit Mahathavorn, who interrogated Samran, said the homeless man had no political motivation for starting the fire – it was an act of negligence.

The fire, which started in a garbage bin underneath the bridge, caused traffic to come to a standstill on February 28 and resulted in months of repairs.

Sanit said police from Thung Mahamek Police Station would interview Samran again on Friday, followed by a re-enactment of the incident that afternoon.

According to police, Samran was the leader of a group of homeless people who cleaned car windows and windscreens for a living at the Henri Dunant and Wireless Road intersections. Samran has previously been arrested for drug dealing and murder.