Police said the cab driver picked up three well-dressed foreign men on Tuesday at 3.30pm. Just half an hour earlier they had robbed a Montblanc shop in Gaysorn Plaza near Ratchaprasong intersection.
The men said they wanted to travel to Suvarnabhumi airport.
Police say they questioned Peerapol Iam-saard, 23, at Lumpini police station, after identifying him as the driver.
Earlier, they picked him up from his home in Bangkok's Klong Tan area.
Police said the taxi driver and the shop owner were not suspected of being involved but were acting as key witnesses in the case.
Pol Maj Gen Suebsak Pansura, commander of Metropolitan Police Division 5, said the driver told them the men, believed to be Chinese nationals, got into his taxi after he had dropped off his previous passengers at Amarin Plaza, opposite Gaysorn Plaza.
While driving to the airport, he dropped off one of the foreign men in front of the Thai Red Cross Society on Henry Dunant Road and later the two other men at gate No. 1 of Suvarnabhumi airport about 5pm.
Police say a closed-circuit television camera at the Ratchaprasong intersection captured images of Mr Peerapol's taxi.
Staff at the luxury goods shop reported the theft to Lumpini police on Tuesday.
They said the men, who spoke Chinese, entered the shop and asked to see some high-end watches.
While the staff were not looking, one of the men snatched a watch — which is just one of eight of a special edition — and put it in his pocket.
The men then left the shop on the first floor of the shopping plaza.
Pol Maj Gen Suebsak said witnesses confirmed the men were Chinese nationals and police were hunting the foreign man who got out of the taxi in front of the Thai Red Cross Society.