The Welshman forms part of a strong Team Sky contingent, and while the 16-kilometre individual time trial suits him, the former maillot jaune is not putting pressure on himself to mount a serious GC bid.
"I think I'll be okay. I won't be at my best but I've been back on the bike for a while and enjoying training," Thomas told Cyclingnews.
"I'm looking forward to a good race, and I've not done it since 2011. I've not raced in the UK that much in the last few years, other than the Olympics, Commonwealth Games and when the Tour was in Yorkshire, so I'm looking forward to that."
Thomas's aims over the eight-day race will be to win a stage and boost his form ahead of the World Championships, where he will aim to compete in the team time trial and individual time trial events.
"Obviously I'll try to win a stage, and finishing in Cardiff will be massive for me. That will give me a massive boost. I think I'll target the odd stage and see how it goes. There are a lot of sprints and I'm sure we'll have someone there for those days."
Moving on from the Tour
Thomas has had several weeks to come to terms with what was a turbulent Tour de France. He pulled on the race's first yellow jersey after winning the opening time trial in Dusseldorf but was involved in several minor falls before eventually crashing out with a broken collarbone. Departing the Tour was Thomas's second Grand Tour withdrawal in a row after he was forced to leave the Giro due to injury.
"Once it's said out loud, that you're going home, it's never a nice feeling," he said, in relation to the Tour.
"It really hits home and then you leave the race behind. It really hits you when you're back home, sitting on the couch and the guys are still racing and you see them on TV. It's hard because you want to be there and it's a massive race. It was a huge disappointment but I just had to take it as a mid-season break. It meant I could eat and drank whatever I wanted for two weeks, until I was back on the bike."
Although Thomas remains focused on his remaining 2017 goals, he has ambitions to lead Team Sky at a Grand Tour in 2018. Mikel Landa has left and the team has not signed a rider with Grand Tour ambitions to replace the Spaniard. With Chris Froome set to defend another Tour title, it leaves Thomas in the potential position of returning to the Giro for one more crack at leading.
"I'll have to see what the route is like before I say I'll target the Giro but we'll see what the other signings are like and see who wants to ride it. For sure, there will be a strong team around me if I think that I can go there and get an overall result but I have to play it by ear. I'd love to do similar races again with Tirreno and also Strade Bianche. It looks like a really nice one to do. We'll have to sit down properly and decide in the winter."