A sacked employee who still lives at Suvarnabhumi airport has been arrested for stealing a bag from a sleeping American traveller.

Suchart Sawatdee, 41, was arrested in the basement area of the airport, outside the Airport Rail Link station, on Sunday evening, tourist police said on Tuesday.

Mr Suchart is accused of stealing the waist bag of John Felton, 30. The bag contained the victim's passport, cash and other valuables.

Mr Felton earlier reported the bag stolen, saying he had put it on his baggage trolley before taking a nap on a bench at the terminal on Sunday.

Surveillance camera footage showed Mr Suchart, in black clothing, taking the bag, police said.

Mr Suchart had previously worked as a trolley collector at the airport, but was fired in 2016 for drinking alcohol on the job.

The suspect told police he had been living in the airport terminal for about two months, eating leftovers and sleeping on benches.

He admitted spending money from the victim's bag to buy a new mobile phone before returning to the airport terminal via the Airport Rail Link and being arrested.