Police said they were interviewing relatives and colleagues of Charlie Kalakicha, 42, to find out why he killed himself. Charlie was part of the airline's ground team at Suvarnabhumi International Airport.
In the Facebook post at about 9.30pm he wrote: "It's time now. Life is so short. Thank you everyone for knowing each other. I need to say goodbye to everyone. It's my time now."
In a one-minute audio message, he asked for forgiveness if he had hurt anyone and forgave everyone who had hurt him.
"You don't know what it's like facing the situation that I am in. It's all blocked up," he said. Police said security cameras captured Charlie parking his car at the building at around 9pm. He then walked through a fire exit and went off camera.