In South Korea, billboards advertising marriages to foreigners dot the countryside, and fliers are scattered on the Seoul subway.

IT was midnight in Hanoi. But after a five-hour flight from Seoul, South Korea, on a recent Sunday, Kim Wan-su was driven straight from the airport to the Lucky Star karaoke bar, where 23 young Vietnamese women seeking Korean husbands sat waiting in two dimly lit rooms.

"Do I have to look at them and decide now?" Mr Kim asked, as the marriage brokers gave a brief description of each of the women sitting on a sofa. Thus, Mr Kim, a 39-year-old auto parts worker from Seoul, began the two-hour process of choosing a spouse. In a day or two, if his five-day marriage tour went according to plan, he would be enjoying his honeymoon.

Increasingly, South Korean men are finding wives outside the country, where a surplus of bachelors, a lack of marriageable partners and the rising status of women have combined to shrink the domestic market for marriage-minded men. Bachelors in China, India and other Asian nations, where the preference for sons has created a disproportionate number of men, are facing the same problem.

The thriving global marriage industry is sending comparatively affluent Korean bachelors searching for brides in the poorer corners of China and South-East and central Asia. The marriage tours are fuelling an explosive growth in marriages to foreigners in South Korea, whose ethnic homogeneity lies at the core of its self-identity. In 2005, marriages to foreigners accounted for 14 per cent of marriages in South Korea, up from 4 per cent in 2000.

After an initial setback — his first three choices declined his offer — Mr Kim narrowed his field to a 22-year-old college student and an 18-year-old high school graduate.

"What's your personality like?" Mr Kim asked the college student. "I'm an extrovert," she said.

The 18-year-old asked why he wanted to marry a Vietnamese woman. "I have two colleagues who married Vietnamese women," he said, adding, "The women seem devoted and family oriented."

One Korean broker said the 22-year-old, who seemed bright and assertive, would adapt well to South Korea. Another suggested flipping a coin.

"Well, since I'm quiet, I'll choose the extrovert," Mr Kim said, adding, "Is it OK if I hold her hand now?"

She sat next to him, though neither dared to hold hands. She spelled out her name in her left palm: Vien. Her name was To Thi Vien.

In South Korea, billboards advertising marriages to foreigners dot the countryside, and fliers are scattered on the Seoul subway. Many rural governments, faced with declining populations, subsidise the tours, which typically cost $US10,000 ($A12,600).