The Welshman, who won the Tour in 2018 but had to settle for second place last year behind Team Ineos teammate Egan Bernal, admitted he was tempted to target the Giro d’Italia in 2020 but wanted to give the Tour 'one more good go'.
Thomas will turn 34 in May before lining up for the Tour at the end of June, and has already spoken this year of his desire to take up triathlon in retirement, which he pencilled in for 'three to four years' time'.
"The Tour will be the big goal for myself again. Obviously it was tough with the Giro as well, because I’d love to go back there at some point, but I just wanted to go back to the Tour one more time as a big hitter," Thomas said in a Team Ineos video.
"At the end of the day, the Tour is the Tour, and I wanted to give it one more good go."
Thomas is also targeting the Olympic Games this year, aiming to earn a spot in the Great Britain squad for both the individual time trial and road race, which takes place in Tokyo just seven days after the final stage of the Tour.
"The reason I fell in love with sport in general was watching the Olympics as a kid in my front room. I always wanted to be part of it – not necessarily cycling but any sport," Thomas said.
"Between the Tour and the Olympics, it’s such a quick turnaround and there’s the time difference as well. Ideally, there would be another week. Maybe the Giro and a different programme might actually suit the Olympics better, but I’ve done it a few times now where I’ve come out of the Tour and gone straight to other races, like the Commonwealth Games in 2014, where the time trial was on the Thursday and the Tour finished on the Sunday. I think it’s just a mindset thing, a lot of it."
Thomas explained he feels much more optimistic about the coming season than he did this time last year. Having won the Tour, his life changed and training was pushed down the priority list last winter, leaving him struggling to find the form he’d had early in previous seasons.
Despite crashing out of the Tour de Suisse, he turned things round to place second at the Tour de France, but this winter he has laid much stronger foundations.
"I definitely feel so much better and different to this time last year," he said. "I’ve started training earlier and I think last year I had easily twice the amount of time off.
"It's totally different, and I'm looking forward to getting stuck into those races, being in the mix, and just enjoying it. Last year, I wouldn’t say it was enjoyable, because it to get to a level where you’re used to being competitive, it just felt like it was a big fight all the time.
"I've just got to go for it – you've got to be in it to win it," he said of the Tour. "That's what motivates me, to go out and give everything I can to get there in the best shape, and once you're there, you do what you can. If I don't win, or podium, or top 10, or whatever, success will just be getting there in my top shape and going from there."