The incident occurred after Thomas missed a par putt on the third round of the Sentry Tournament of Champions in Hawaii.
‘I am an adult. I am a grown man. There is absolutely no reason for me to say such a thing.
“It’s awful. I’m so embarrassed. It’s not the kind of person I am … But unfortunately I did and have to admit it and apologize very much.
“I apologize to anyone and everyone I have offended and it will make me better,” Thomas added.
“As he said after his round, we agree that Justin’s comment was unacceptable,” the PGA Tour said in a statement, according to the AFP news agency, which added that Thomas will likely be fined for conduct “unbecoming a professional” .
Going into Sunday’s final round, Thomas is tied for fifth place, four shots behind co-leaders Harris English and Ryan Palmer.