Turner said: "Once the Scarlets made their decision, we began our homework on Gavin. It had been said he had an Achilles injury but that hasn't shown up in training for us.
"The information I received about Gavin was good including some feedback from Colin. "He was enthusiastic and said he had always rated him really highly - I was pleased by that.
"I'm delighted to have captured Gavin because it will bolster our pack as we've lost Colin, Richard Parks and Jamie Ringer."
Thomas left the Scarlets after the west Wales region cancelled his contract following a 26-week injury get-out clause.
Now Thomas, capped 22 times by Wales, hopes to resurrect his career alongside fellow new signings Rob Sidoli, Ali McKenzie and Kiwi pair Ben Castle and Danny Lee at Rodney Parade.
Turner added: "Gavin is a top class rugby player and I've watched him a lot since he played for Bath. "He's experienced, a good ball carrier and his defence is excellent. They are all qualities are all traits that I look for in a player.
"I'm confident he will suit our style of play by getting his hands on the ball and bring a new dimension to us."
The Dragons begin their season preparations with friendlies against Worcester and Coventry after a week-long training camp in west Wales next week.
Turner added: "We're going away to Abersyswyth university for some hard rugby training and team-bonding exercises.
"It's a good opportunity for us to get together and in the days of teams heading off to Europe on planes, we will be going on a bus trip. I'm looking forward to it."