There are 30,000 professional child Muay Thai fighters in Thailand. They fight to support their families, to pay for food and school books, to keep their brothers and sisters in education.
Some begin their professional careers at the age of 7, and fight for as little as £4 a match. Betting on the fights is where the big money can be made, and lost. Gamblers say they like child fights because they fight with 'pure hearts' - they're less likely to throw a match, the fights are more unpredictable and the kids really go for it.
The big money is made by sponsors, fight organisers and promoters. It's not illegal for children to fight professionally, as long as they have their parents' permission. They should wear protective gear, and not fight more than once a month, but the regulations are regularly ignored.
Muay Thai is a noble martial art, with a 700 year history. It's a part of Thai culture, and top boxers are celebrated as heroes in their communities. But many believe that professional child fighters are vulnerable youngsters being exploited for profit. Their wellbeing becomes less of a priority than the money that could be earned.
And evidence from a study being conducted in Bangkok, scanning the brains and comparing cognitive function of child boxers to similar kids who don't box, shows that the damage sustained from head blows reduces IQ, increases the risk of dementia, and reduces capacity to learn and remember. Professional Muay Thai, where children are fighting and training with a high level of intensity and frequency, is causing brain damage that will have permanent effects.
I travelled to Isaan, in the north east of Thailand to meet 11 year old Nat Thanarak as he prepares for the biggest fight of his life.
A 2 minute short from the film is available on YouTube:
Watch the full film at www.Channel4.com/UnreportedWorld/4oD
Check out a photo essay from the shoot: Images
For more background and links to organisations that can help, see Related links