Thomas's manager Emanuele Palladino told Wales On Sunday that the Wrestler star also wants to learn Welsh for the sporting biopic.
"Mickey wants to film everything in Wales, although it is early days," Palladino said. "He really wants to throw himself into Welsh and rugby and really learn as quickly as he can. He'll learn Welsh I think, obviously where it is relevant as well.
"He is going to get rid of his two front teeth and stuff - he will be taking them out. Mickey intends to get as close to the character as he can, as he thinks it is a great story."
Rourke has been working on a movie about Thomas since last July. The Oscar-nominated actor recently revealed on Alan Carr: Chatty Man that he admired Thomas for performing at rugby's highest level while keeping his sexuality a secret.
Thomas, who is the most capped player in Welsh rugby history, announced publicly that he was gay in December 2009. He is the world's only current professional team sport athlete who is open about his homosexuality.