The man stirred passenger and online alarm over the airport's and the airline’s security measures after he managed to enter the plane’s passenger cabin without having a ticket or boarding pass.
The official, who asked not to be named, said the man was a mentally ill person who regularly strolled around the airport.
The official said the man once tried to enter a restricted area and he ordered his subordinates to take him away from the airport grounds.
The man often claimed that he would travel to meet fugitive former premier Thaksin Shinawatra and even members of royal family, he added.
The source said he would recognise the man but the incident occurred on the day that he was not working, or he would have prevented him from sneaking aboard the Nok Air flight. The source said the incident resulted from a security blunder at two passenger screening checkpoints, one manned by the airport officials and another by airline staff.
He said the plane sneaker told an airport official at the first checkpoint that he was a friend of the plane’s pilot and would like to see him. The official, who allowed him to pass the checkpoint, was a new employee who had been working for only three days.
“In addition to the airport’s passenger checkpoint, another checkpoint manned by Nok Air employess also was lax in security. They did not inspect passenger's ticket and ID card as usual. They are suppposed to tear off part of the boarding pass before allowing passengers to go through the door leading to the bridge connecting the plane and the terminal,” the source said.