Hong Kong, China (CNN) -- Aki Ra was forced to be a child soldier in the genocidal Khmer Rouge regime in Cambodia in the early 1980s, taught to shoot a gun and plant deadly landmines.
He was later seized by the Cambodian army and the Vietnamese, who were fighting together against the ultra-Maoist Khmer Rouge, and he again planted explosives in the ground as war raged in the Southeast Asian nation.
Years later, when the United Nations came in to help restore peace to Cambodia, Aki Ra decided he needed to undo the damage he and others had done, so he began demining on his own after spending a year training with U.N. deminers.
"I have the idea from the U.N. to help make peace in Cambodia in 1992-1993, stop fighting, stop lay landmine," he said on a recent visit to Hong Kong, where he talked with students about his life and work. "I try to change from bad -- I want to be a good thing -- so I clear landmine to help make my country safe."
Aki Ra, who believes he is about 40 years old, embarked upon a course that would change his life. He said he set off as a lone deminer, clearing some 50,000 mines and unexploded ordnance, according to his own count.
"I didn't have any equipment ... I clear by knife, by stick," he said. "I go into the very big minefield that has many mines or bombs. People tell me they saw many on the ground. ... I go and I dig around. I take and I unscrew detonators from the mines. I keep in my pocket," he said as he explained the procedure, which has killed others, noting for him, "It's not dangerous, easy."
Over time, he set up a landmine museum in his home in Siem Reap, which is home to the famed Angkor Wat temples and was caught up in the years of fighting. He has defused land mines and other unexploded ordnance, and AK 47s, on display.
"I had an idea to open a landmine museum to teach people to understand about war, landmine," he said. "Even though the war finished, (these explosives) still kill people and the land cannot be used."
The museum, located near the Banteay Srei temple in Siem Reap, had welcomed 4,000 to 5,000 visitors a month until the global recession hit in 2008, said Bill Morse, a Californian who works with Aki Ra. In the last year, those numbers have fallen to 3,000 to 3,500.
Heng Ratana, director general of the government's demining agency --- the Cambodian Mine Action Centre --- said the major period of landmine use in the country was from 1970 to 1998, a period that covered civil war, take over by the Khmer Rouge, invasion and occupation by the Vietnamese and further fighting between the government and Khmer Rouge after the Vietnamese left.
Ratana said 500 square kilometers of the country have been cleared of 2.5 million landmines and unexploded ordnances, but 2,500 square kilometers of the land remains contaminated.
"We plan to clear Cambodia from the impact of landmines in the next ten years," he said, noting it was a "big job." "You can see landmines in Cambodia remain a serious threat, not just to personal security but also to social and economic development in the country as well."
Cambodia is one of the most heavily mined countries in the world, according to the International Campaign to Ban Landmines. Ratana said some 200 to 300 Cambodians are injured or killed every year by landmines and unexploded ordnance even though the fighting ended years ago.
"Many of our Cambodian people living in the rural areas, their day-to-day lives are challenged with these remaining items (landmines)," he said, noting some fields of rice, corn and cassava in remote areas or near villages may still be contaminated.
Four main groups are demining in the country, with help from smaller outfits, such as Aki Ra's Cambodian Self Help Demining non-profit organization. Ratana said about 5,000 deminers are working in the country and though he has not met Aki Ra before, efforts by small, trained groups are welcome.
"Whoever can contribute to this effort will be contributing to this national mine clearing effort in Cambodia," he said. Aki Ra, with the help of some foreign volunteers, founded his demining group in 2008 --- when he also got his formal certification to remove landmines and other unexploded ordnance.
The government and other large demining groups had not approved of Aki Ra's way of removing landmines --- without protective gear, among other things --- and wanted him to operate in accordance with international standards, including reporting on the number of explosives removed, to which he agreed, said Morse, who is international project manager of Aki Ra's group.
"There is no doubt that a lot of what he does is penance for what he has done in the past," said Morse, who first met Aki Ra while he was visiting the museum. "I've talked to him about it before, and certainly that is a part of it. He has done a lot of bad stuff and now he wants to do good."
"He is certainly not a saint. He is no different than you and me. I think that's what impressed me with him so much," added Morse, who is also president of the Landmine Relief Fund. "He is just a regular guy like the rest of us are. He has just had an opportunity to do something that can really impact his country."
Since 2008, Aki Ra has cleared four villages of about 100 deadly explosives. He chose to focus on smaller communities rather than densely-populated areas.
"Some villages, they wait five years, a few years, no people (deminers) come. They clear by themselves," Aki Ra said, noting that one of his friends has been struck by landmines seven times --- on the same leg --- and has fortunately survived.
"I feel good, I feel better because I can help my country, even if I cannot do the entire country," he said.
Aki Ra's group has 10 deminers, including one who lost his parents and one of his legs to landmines and who has lived in an orphanage Aki Ra built on the museum grounds.
Aki Ra started taking in children in 1997. About 25 youth --- some injured by landmines or born missing limbs, some orphans, some from poor families -- live there now.
The children receive schooling onsite and are also transported daily to a local school; some of them receive physical therapy, too.
Aki Ra plans to continue pulling land mines from the ground until the country is free of the explosives.
"I just like to do what I can," he said. "I want change from poor, from bad to good, not same as me before --- I want my country like that, in the future."