Thiem broke the Grand Slam stranglehold of Roger Federer, Rafa Nadal and Novak Djokovic by winning the 2020 US Open but the injury sidelined him for months and other niggles saw him slip down the rankings to number 352 last June.
After a first-round exit at the Australian Open in January, and disappointing performances in the tournaments that followed, Thiem made the quarter-finals of the Estoril Open and beat Richard Gasquet 6-1 6-4 in his opener in Monaco.
"Some positive signs happened already in Estoril and today (Monday), I had the feeling that I was doing from time to time good damage with both forehand and backhand," said Thiem, who next plays Holger Rune.
"The power wasn't there last year even when I started to win matches and played better. In the inner season the power wasn't there yet. Also maybe not in the beginning of the year.
"In the last month it's coming back, especially in practice. The shots are there, the power is there like before, but I was using it wrong. There's full trust again in the wrist and the forehand."
A return to top form on clay would be an encouraging sign for the world number 106 ahead of the French Open, where he reached the final in 2018 and 2019 before losing to Nadal on both occasions.
After announcing at the weekend he had split with coach Nicolas Massu, Thiem has joined up with Benjamin Ebrahimzadeh and hopes the partnership will bear fruit.
"There wasn't a lot of time," Thiem said. "I needed a coach right away so we decided to start the relationship and give it a try."
