That is what this report is claiming:

Autism spectrum disorders (ASD) in South Korea affect an estimated 2.64% of the population of school-age children, equivalent to 1 in 38 children, according to the first comprehensive study of autism prevalence using a total population sample. The study — conducted by Young-Shin Kim, M.D., of the Yale Child Study Center and her colleagues in the U.S., Korea and Canada — identifies children not yet diagnosed and has the potential to increase autism spectrum disorder prevalence estimates worldwide.

ASDs are complex neurobiological disorders that inhibit a person’s ability to communicate and develop social relationships, and are often accompanied by behavioral challenges. Published online in the American Journal of Psychiatry, the study reports on about 55,000 children ages 7 to 12 years in a South Korean community, including those enrolled in special education services and a disability registry, as well as children enrolled in general education schools. All children were systematically assessed using multiple clinical evaluations. This method unmasked cases that could have gone unnoticed. More than two-thirds of the ASD cases in the study were found in the mainstream school population, unrecognized and untreated. [Science Daily]

For comparison sakes the Center for Disease Control in the US says that 1-110 US children have been diagnosed with autism. I have to wonder if differences in reporting or standards in what constitutes autism could explain such a huge difference between the two countries?