Here's more proof Mike Tyson didn't have a care in the world after beating up an alleged heckler on a plane last week -- with the boxing legend laughing his ass off on the phone moments after the incident.
TMZ Sports has obtained video of Iron Mike in the San Francisco International Airport after being escorted off his plane to Florida around 10:49 PM on Wednesday ... and the former champ looks happy as a clam as he chats it up on his cell.
A witness tells us Tyson was surrounded by cops .