The 25-year-old centre or back rower is the older brother of Wales rugby union international Matthew Morgan.
Tom Morgan has also played rugby union, having turned out for hometown club Bridgend Ravens, as well as Bridgend Athletic, Neath, Swansea and Bristol.
He has played for the Scorpions before, having spent two brief spells with the rugby league outfit in 2011 and 2015.
“I had a successful trial period with Bristol this summer, but we couldn’t agree terms,” Morgan said.
“Now I’m glad to be back playing rugby league, the game I love watching and playing. I’m looking forward to a big pre-season and for the challenge of what 2016 season is going to bring.
“Hopefully we can make a big push for promotion with the new players added to squad and financial backers coming in, and make rugby league a big force in South Wales.”
The Scorpions have also confirmed that Jordan Sheridan and Dafydd Hellard have signed new deals at the club.