Australian boxing great Jeff Fenech is in a Thailand hospital and may need heart surgery.

The three-time world title winner was training Sydney fighter Jack Brubaker and some other boxers in Bangkok but after coughing up blood was forced by his students to seek medical attention.

In a video from his hospital bed, an emotional Fenech, 55, said he had an infection on a valve near his heart and he felt he had let down his young charge.

A film crew from Boxing Epicentre have been following Fenech as he trained Brubaker and some other young fighters.

"I've got some pretty bad news, I've got an infected valve that's connected to my heart," Fenech said.

"Which means for the next few days they will try to get rid of the infection then I'll need to have surgery.

"I feel really bad towards Jack and the rest of the team. I love you guys."