By Neil Smith BBC News entertainment reporter

Beautiful Boxer tells the story of Thai kickboxing star Nong Toom

Beautiful Boxer tells a story so odd it has to be true.

Parinya Charoenphol (also Kiatbusaba) was born a poor nomad who spent much of his early life in a monastery.

Realising he had a flair for kickboxing, he became a master at Muay Thai, the most traditional and revered form of the ancient martial art.

Feared by his opponents for his swooping kicks and devastating elbow blows, he became one of Thailand's best-known boxers - and its most controversial.

For Charoenphol, or Nong Toom as he became known, was a transsexual who wore make-up in the ring and dreamed of saving enough money for a sex change operation.

"For me, Nong Toom is like a walking paradox," says Ekachai Uekrongtham, the Thai-born director of Beautiful Boxer.

"He set out to master something that is totally masculine in order to become totally feminine."

Nong Toom would eventually realise his dream, having gender reassignment surgery in 1999 at the age of 17.

Forbidden to return to the ring - Thai women are not allowed to kickbox professionally - she now lives as an actress and model in Bangkok.

'Prejudiced'

"My initial reaction towards her was quite negative," says the director.

"Thais hold kickboxing in very high regard, and I felt she had tarnished its image.

"It was not until I met her that I realised I had been very prejudiced against her, without giving her a chance."

Real-life kickboxer Asanee Suwan plays the lead role in the film

Nong Toom played a significant role in the scripting process, though there was never any chance she would play herself on screen.

Nor, says Uekrongtham, did she have a veto over how she would be depicted. "I told her from the start the film would not put her on a pedestal.

"This is fiction, a biopic. I wanted to capture the essence of who she is, in a way that would contribute to the themes I was interested in exploring."

One of the hardest aspects of production was finding an actor who could convincingly portray the contrasting sides of Nong Toom's persona.

Indeed, the director admits the problem almost proved unassailable.

"I decided very early on I wanted to cast a real kickboxer," he says.

I think he was man enough to be a woman Director Ekachai Uekrongtham, about actor Asanee Suwan

"It's a skill you need to acquire over a lifetime, so I wanted it to be authentic.

"But kickboxers are not usually good actors - they are trained not to express their feelings in the ring."

Fortunately, Uekrongtham found his ideal candidate in Asanee Suwan, a real-life kickboxing champion who has fought in almost 200 matches in Thailand and Denmark.

Suwan spent a year preparing for the role - taking acting, movement and ballet classes and losing weight in order to look more "feminine".

The film has won awards at film festivals around the world

He was also required to adhere to a strict skin and body care regime - including numerous body scrub and hair removal sessions.

"Asanee had not acted before, but I felt he was brave enough to explore some emotional realms he may not have been comfortable with," the director says.

"I think he was man enough to be a woman, to be cool about it and take artistic risks."

For while Nong Toom's story is a compelling and unusual one, there were wider issues Uekrongtham wanted to address.

"I wanted to do something to do with the ever-changing concepts of what it means to be a man and what it means to be a woman.

"It was an amazing story to use as a springboard to talk about those subjects."