Better known as Dan Pontypridd, or as Dan yr Union, Thomas was born at Pwllgwaun near Pontypridd.
He was engaged in huge, epic mountain fights, both close to his home and in the London area.
The Welshman, who carried a feared right to the ribs, tended to take enormous amounts of punishment early on in a fight before coming on strong.
Thomas retired to Porthcawl, where he met and gave advice to a fast-rising Freddie Welsh.
The former brawler became a reformed character and a pillar of the community, and was a critic of boxing in his later life.