He says he was shooting with other actors near Phi Phi Island. The action director Jack Gill had planned out a stunt in which the jet-ski chase was suppose to be shot from a chopper.
"Initially, as we started filming and moving around in the shallow waters, the waves were moderate... so we decided to move ahead in the deeper waters since the scene required a proper aerial view which should look like a chase from a top angle, " Ajay wrote on his blog www.ajaydevgan.net.
He was shooting with four other stuntmen.
"They were moving aggressively in the sea trying to give their best shots by manoeuvring with their cuts around me... The chopper was also hovering right above us and as close as possible to us to get better shots, " he added.
According to Ajay, all seemed to go well until they realised they were nearing another smaller rocky island called Maya Bay.
"Suddenly the weather started to change. The wind and the waves were trying to show us their stunts and our guys instantly thought of retreat.
"A sudden gust of strong wind hit me and next moment the chopper above us lost control and blades were so dangerously close to us that we could feel the strong whipping winds of our helicopter, " he described.
Ajay, who featured in several action movies including his debut vehicle "Phool Aur Kaante" and "Raju Chacha", says this incident will be etched in his mind for a long time.