There is no doubt in Joe Cole’s mind that working on the feature film “A Prayer Before Dawn” has been the most demanding acting job in his career.

“I knew going into it that it was going to be hard, having seen (director) Jean-Stephane’s (Sauvaire) previous movie, ‘Johnny Mad Dog,’ about soldiers in Liberia,” Cole says. “He has quite a documentary style. He told me the fighting is going to be real and that he was going to shoot in real prisons with real prisoners.

“His plan was to make a movie that was as close to the truth as we possibly could.”

Cole plays Billy Moore, a young English boxer who gets caught dealing drugs and is sent to two of Thailand’s most notorious prisons. The one escape Moore has from gang violence is to be part of the Muay Thai boxing tournaments featuring prisoners.

It is an escape from the prison gangs, but one that almost costs Moore his life because of the brutality in the ring. The script is based on Moore’s book, “A Prayer Before Dawn: My Nightmare in Thailand’s Prisons.”

Along with being his most demanding job, working on “A Prayer Before Dawn” was also his most satisfying. He wants to believe another role might push him even more, but if that part never comes along, Cole can live with the idea that playing Moore tested him to the max.

The 29-year-old London native has appeared in a variety of television series, stage and movies since leaving the National Youth Theatre. His credits include “Peaky Blinders,” “Green Room,” “Skins,” “Offender” and “Black Mirror.”

The only way “A Prayer Before Dawn” would be believable is if Cole looked as confident delivering a kick to the face as he did saying his lines. To prepare, Cole started training in the United Kingdom and continued his work in the ring while he was in Atlanta filming “Thank You for Your Service.”

He arrived in Bangkok three months before filming was scheduled to start, where he trained in what he called “sweat and sawdust” boxing camps. Cole didn’t take the route of a Hollywood actor of spending most of his time in the comfort of an air-conditioned trailer during his workouts in Thailand. Not only did he spend most of his time in the ring, he also went through the same rituals as the Mauy boxers, down to cleaning himself using only a bucket of water.

Once he arrived in Thailand, Cole was surrounded during his training and in the filmed fights by real boxers. He could have been looked at as the outsider trying to muscle into their world, but the relationship between Cole and the real boxers generally went the other way.

“I think they were respectful as we developed a real comradery. To make sure the fights looked as real as possible, I had to trust those guys,” Cole says. “There certainly was an element of people trying to prove themselves. Their masculinity was threatened by this white guy from London with a camera crew.

“But that was part of the fun of it.”

“A Prayer Before Dawn” is available now on DirecTV and is in theaters.