Thomas was on the 4th green during the Sentry Tournament of Champions in Hawaii on Jan. 9 ... when he missed a 5-foot par putt and muttered, "f*****."

Thomas immediately apologized after the round ... saying in a post-play interview, "There’s just no excuse. I’m an adult, I’m a grown man. There’s absolutely no reason for me to say anything like that."

Thomas, though, has faced huge backlash despite the mea culpa ... and on Wednesday, he said he intends to enter a training program to help him learn from it all.

"It’s not a word I use,” Thomas said, “but for some reason it was in there and that’s what I’m trying to figure out -- why it was in there."

“And like I said, it’s going to be part of this process and training program, whatever I need to do, not only to prove to myself but to prove to my sponsors and prove to the people who don’t know who I am that that is indeed not the person I am.”

The 27-year-old golfer declined to elaborate on what the program will entail ... saying only, "Obviously people are going to be a part of that process."

"But what I’m doing I’d like to keep internally and just go through the appropriate steps to get where I need to be and want to be, so people understand that’s not the person I am, the character I like to portray."

Thomas has lost sponsors over the incident ... with Ralph Lauren dropping the golfer last week after having a longstanding relationship with him.

Thomas said he was "upset" over losing the clothing company ... saying he wished they had stuck with him while he worked to fix his issues.

"I spoke with them, along with all my sponsors, and although I apologized, just like it was then it’s an opportunity for me to grow and I felt like it was something we could have done together and gone through that process," Thomas said.

"They just felt like they needed to move on so that’s exactly what I’m doing as well."