Jean-Stéphane Sauvaire’s prison drama, A Prayer Before Dawn, is based on the true-life account of troubled British boxer, Billy Moore, which he detailed in his bestselling novel of the same title. Moore was sent to two of Thailand’s most notorious jails and became immersed in a world of drugs and gang violence.  Refusing to die in prison, Billy becomes a student of the lethal art of Muay Thai Boxing, and in the process, finds a brotherhood that will guide him on an incredible journey to redemption.

During his stop at the Deadline Studio at SXSW, Sauvaire shared how it was challenging but necessary to shoot at an actual Thailand prison and use real-life former prisoners.

“For me, it was important to be realistic. I like mixing the documentary style with fiction so I really wanted to shoot in the prison with former prisoners,” said Sauvaire adding that only they “could give the sense of how is the life in prison,” which he said was much help during the process of shooting the film.

Aesthetics also played a big role. “These guys are all covered with tattoos and you can’t imagine coming on set and having the extras and doing the makeup on 100 people so they were perfect physically.”

Sauvaire also shared that Moore was very involved with the film adaptation, although he could not be on set physically.

“When we were working on the script, we could call Billy and say how it was, how did you react at this time, how would you react if this happened. It was a challenge but at the same time was really helpful. Billy was really with us helping a lot.”

To see more of the interview check out the video above.

The Deadline Studio at SXSW 2018 is presented by MoviePass.