The incident occurred about 8am yesterday as the two men passed through an airport scanner one after another, leaving their hand luggage items in plastic trays to move through a second scanner.
The pair had both been processed by Immigration, ready for their flights off Phuket.
The Italian man collected all items from his tray on the departure lounge side of the scanners, but overlooked his mobile telephone.
According to police, the Frenchman spotted the mobile telephone and picked it up, neglecting to tell the Italian that he had forgotten his phone.
A short time later, as both men sat in the departure lounge waiting for flights, the Italian realised he had forgotten to pick up his mobile telephone.
He went to airport authorities who checked security camera footage. The video showed the Frenchman picking up the Italian man's telephone.
Airport police confronted the Frenchman in the departure lounge.
He was arrested and taken for questioning.
The mobile telephone was returned to the Italian man, who caught his flight out of Phuket on schedule.
The Frenchman, who had been aiming to fly to Paris with a Thai girlfriend at the end of a 30-day stay on Phuket, missed his flight.
Instead, he was taken to Tachatchai Police Station and charged with theft.
He faces a wait in custody for a court hearing and a possible sentence to overcrowded Phuket Prison.
Earlier in the week, airport worker Danai Buthjaw, 27, was arrested and charged with stealing a pair of distinctive bright pink runners from the luggage of a woman passenger who had just arrived on Phuket from Bangkok.