The man recalled being touched three times and told the court: "I believe I said: 'What the f*** are you doing? Stay away'.
"The first time was the feeling of a light breeze on my thigh. I felt it again and saw the same guy walking back to his seat. It was a light touch on my thigh, the inner thigh.
"Something happened again and I caught the hand. It was in the crotch area.
"He mumbled and stumbled. I saw embarrassment on his face, shocked that he had been caught. I think that he might have been drunk."
Kathy Hirst, prosecuting, said: "The complainant, who was travelling alone, noticed another gentleman in a distinctive pink shirt walked down the aisle and 'clocked' him.
"There was eye-contact and he held his gaze."
She said the first incident occurred four hours after taking off from Heathrow, with Speak, a BA employee, using his staff points to fly.
Miss Hirst said: "On two occasions the complainant says he was touched above clothing on his penis.
"He was woken by someone running his hand over his thigh area, near his crotch. He raised his eye mask and saw the man in the pink shirt retreating.
"It happened again forty minutes later. The hand went up towards his waistband and it seemed to be prolonged.
"He saw the same man in the pink shirt walking up the aisle."
The passenger reported Speak to the cabin crew and a member of staff spoke to the defendant.
Miss Hirst added: "It was obvious to her he was drunk and she told him a complaint had been made. His eyes rolled and he fainted and fell to the floor."
Speak, who denied touching the passenger, was questioned by police on his return to the UK.
He disputed the allegations and accepted he was wearing a pink shirt but added he took a sleeping pill and had a few drinks before take off on October 12 last year.
Speak received a 12-month community order, which includes 160 hours community service work, and must pay £400 costs. He was also made to sign the sex offenders register for five years.
Recorder Bruce Houlder QC told Speak: "Whilst the internal aircraft light was dimmed and while you thought the complainant was asleep you twice moved your hand up his leg and touched his penis over clothing.
"The touching appears to be brief and the second time the passenger complained to the crew and you remained in a seat reserved for crew for the remainder of the flight.
"Fortunately for you it was reported to the UK police rather than the police in Thailand.
"You were a manger with British Airways, you must have been aware of the gravity of the offence you were committing and the staff knew who you were.
"You did falsely suggest the complainant was mistaken in that you touched him and you have not expressed remorse of any kind."
Speak is now unemployed after BA sacked him after an internal disciplinary hearing before the trial.