The former world number three struggled to get back to top form after suffering a wrist injury in 2021, which sidelined him for months, and the Austrian fell out of the top 300 in 2022.
The twice French Open finalist finished 2023 ranked 98th in the world, and while he hoped to continue his rise with a decent run at the Australian Open, he bowed out in the first round.
"I see this as my last chance. If I make it, it can happen quickly," Thiem told Austrian daily Der Standard on Tuesday.
"I've been back for two years now since the injury, and I finished 2022 on 100 or so and last year on 98. If I finish the year on 100 again, you have to think about whether it's still worth it.
"I've been in rankings for two years now that I don't want to be in. Of course that weighs on me ... I've been chasing the feeling of really being able to play tennis in a match again for a long time. And the way I expect myself to."
Thiem also said he had parted ways with long-time coach Benjamin Ebrahimzadeh.
