By Ulli Schauen
Reporter, Crossing Continents
About 16,000 South Koreans work in foreign countries as Christian missionaries. Only the US sends more people abroad to win converts to Christianity.
Christianity and Buddhism share the skyline in Sihanoukville
In the city of Sihanoukville, Southern Cambodia, I found Korean Protestant missionaries competing with one another, trying to convert locals to their own Protestant denomination.
But the missionaries don't just offer Christianity.
The Kompongsom Taekwondo Federation in Sihanoukville is sponsored by the Presbyterian Yangmoon Church in Taegu, South Korea.
It is run by retired military commander Kim Ka-Jung, who offers Taekwondo classes to young Cambodians. After class, the youngsters sing hymns and listen to a sermon.
The missionaries call this the "contact point" method of conversion. Potential converts are offered lessons or accommodation before being presented with the message of the gospel.
Downstairs is the Kompongsom Bible Presbyterian Church run by Pastor Moses Hahn and his wife Grace.
Mr Hahn offers free English lessons, food and accommodation in his "Bible School", where he trains young non-Christian Cambodians to be pastors after only three years. He says they are usually baptised after six months.
A former factory worker who is now a third-year student, tells me she is happy to have been offered free food, lodging, and some education.
Hahn's Bible School offers free food, lodging and English lessons
It is more than she could have expected from her job in the textile factory.
A few kilometres away, the first Christian University of Cambodia has been set up by another Korean missionary, Reverend David Gu.
From a huge building erected at the foot of the Buddhist Pagoda of Sihanoukville, he aims to educate "a new Christian leadership" for Cambodia.
David Gu says his Christian University of Cambodia has 600 students of all grades, from nursery to college.
At the Taekwondo Federation, 200 children attend the Sunday school. Downstairs in the Bible school, Pastor Moses Hahn boasts 60 students, as well as 50 graduates who are working as pastors around the country.
These success stories are well received by congregations in South Korea, who are happy to keep providing money to keep the missionaries at work.
And many church members in South Korea go a step further, signing up for visits to Korean missions abroad - so-called "camcorder missions".
One such group was kidnapped in Afghanistan in 2007 by the Taleban. Two members of the group were killed.
Many of the Korean Protestants I have spoken to, consider them to be "martyrs" whose "blood" is good for the cause of Jesus in Afghanistan.
Every Christmas, hairdresser Lee Soo-Young travels from Seoul to Phnom Penh with her family, a pastor from her church and other church members, to visit the congregation they support.
Treating children for lice is one of the ways the missionaries reach out
The five-day trip costs about $10,000 for a group of eight, but the group thinks the personal contact is worth the effort and expense.
When I ask them if they would travel to serve God's cause in a dangerous country like Afghanistan, all but two hands are raised.
Korean missionaries tell me that after decades of war, civil war and turmoil, Cambodia is open to evangelisation. Buddhism is seen as having been weakened by decades of war and the anti-religious regime of the Khmer Rouge.
The number of Korean Christian missionaries in Cambodia has risen in recent years to at least 400.
Key to prosperity
The missionaries claim that conversion is not only the key to a life according to God's will, but also to prosperity.
They cite South Korea as an example, where a rapid Christianisation has accompanied rapid industrialisation.
Moses Hahn, for example, has only one explanation for the huge disparity in wealth between North and South Korea.
"There is only one reason. They have no God, but we have God - true God," he says.
Korean congregations fund churches including So Kom's
So Kom is a Cambodian pastor who graduated from Moses Hahn's bible school and was sent to a nearby village to "plant a church".
His modest wooden church building was built with funds from Korea. On a monthly budget of $120 for himself and the church's operations, So Kom is expected to offer English lessons as well as spreading the gospel.
But it is now in competition with an English language school that was set up across the street. Unlike the church school, this one is authorised by the government to issue certificates of attainment.
Now church members are leaving for the rival school.
"My church is already dying," says So Kom.
It makes me wonder whether Chan Thuch, abbot of the Buddhist Pagoda in Sihanoukville, will be right after all. The head monk is still very confident about the future of Buddhism in Cambodia.
"It is the poor who convert to Protestantism," he says. "But once they are better off, they will return to Buddhism again."
Reporter Ulli Schauen from Deutschlandfunk travelled to South Korea and Cambodia for BBC Radio 4's Crossing Continents.
Crossing Continents reports on the rise of the Korean Missionary on BBC Radio 4 on Thursday, 27 March at 1100 GMT, repeated Monday, 31 March at 2030 GMT.