An Indian-flagged Jet Airways plane made an emergency landing at Suvarnabhumi airport on Wednesday night after two passengers spotted an unattended mobile phone displaying the message "do not turn off".
The discovery was reported to the captain of flight 9W 66, who took it for a bomb threat and immediately informed the control tower at Suvarnabhumi airport.
The plane had departed from New Delhi airport with 153 passengers onboard and was due to land at Suvarnabhumi at 8.37pm.
Suvarnabhumi airport director Sirote Duangratana said after receiving the captain's report it was decided to implement the "emergency plan to deal with a bomb threat".
The airplane was directed to an isolated parking bay after landing. The passengers and eight crew members were subject to strict examination and all luggage was checked thoroughly by the airport's security and officials from the Explosive Ordnance Disposal unit.
An Indian couple later told police they had found a phone showing a "do not turn off" message on one of the passenger seats, and asked a flight attendant to locate its owner. The phone was taken to the captain, who reportedly feared turning it off might detonate a bomb.
Pol Maj Gen Surawhet Hakphan, commander of the Patrol and Special Operation unit, said the incident had not been taken lightly. A full search had found no suspecious objects.
He said the couple had acted correctly, with good intentions, and were not suspects.
It was not known who the phone belonged to.