Thomas, a former Wales Under-20 international, was released from the Dragons after serious injuries to both of his knees knocked his development back.
Coombs too was looking to establish himself at the Welsh region but told Thomas he'd be back - as long as he knuckled down.
The Dragons skipper has certainly heeded his own advice - the forward has since been capped ten times for Wales - and 23-year-old Thomas, who penned a one-year deal at Rodney Parade earlier this week, is hoping to similarly seize his opportunity back at the club and star in the GUINNESS PRO12.
"Coombsy spoke to me when I got dropped and told me to go out to the Premiership, play well and force my way back," Thomas told the South Wales Argus.
"I was injured at the end of my contract and he gave me some confidence, saying that I would get noticed if I did well. He said that the chance would come round again and that's what has happened.
"I wasn't playing well when I first came back from injury but then my form started to get better and I started to think of going full-time again.
"I didn't know whether it would be back at the Dragons or elsewhere, but the opportunity to return came up and I grabbed it with both hands. It's good to be back."
Follow us on Facebook, join the conversation on Twitter, sign up to our YouTube channel for extensive match highlights and sign up for our newsletter for regular updates on the GUINNESS PRO12.
Guinness PRO12
Suite 208, Alexandra House,
The Sweepstakes
Ballsbridge, Dublin 4, Ireland