I've searched and searched and haven't found any evidence he went to North Korea. This article from Fortune mentions that Kim Woo-jung (the CEO) claimed the President (Kim Dae-jung) told him to leave the country for a short while and allow restructuring and that he wouldn't be prosecuted. How much of it is true? Impossible to tell. Korean companies have always been in bed with the government so it's definitely plausible, but who knows. Besides, talking about Daewoo and this is within the 20 year rule, so no more about that.

On to your real question, did anyone else defect into the North. Sure! Just off the top of my head, I remember a pig farmer in the eastern province of Gangwon-do who crossed through the DMZ and the minefields into the North. Here is an article about it that also mentions a few others who had tried to defect to the North. I don't remember the exact situation, but the pig farmer had been accused of a crime - theft or some sexual misconduct I believe. But again, this is all within 20 years, so no more about this.

The most notable case would be of Oh Gil-nam. He defected from the South to the North in 1985 with his wife and two daughters. An economist, he was living in Germany at the time and was influenced by leftist Koreans living there who suggested he could help North Korea with his knowledge of economics. Of course, upon arriving in North Korea, things were not as promised. Oh and his wife made propaganda broadcasts and studied Juche ideology. Oh was allowed to leave in order to recruit more people to come to the North, but his wife told him not to do it. She told him to pretend that she and his daughters had died in a car accident and to flee. Upon arrival in Denmark, Oh requested political asylum where he stayed before returning to South Korea in the early 90s. His wife and daughter were placed in Yodok concentration camp and, as of a few years ago, were thought to still be alive. The North Koreans sent Oh letters from his family for a few years and tried to entice him back but to no avail.

Another big name was Choe Deok-sin and his wife, Ryu Mi-yong. Choe was a general during the Korean War. After the war, he was an ambassador and foreign minister under the Park Chung-hee government until he fell out of favor in the 70's. He and his wife lived in exile in the United States until they defected to the DPRK in 1986. Choe died a few years later in 1989, but his wife lived in North Korea until just last year.

Besides defectors, there are double-defectors; North Koreans who defected to the South who then return to the North. North Koreans are treated very poorly in South Korean society for a variety of reasons. Many of them find that their North Korean education is years or decades behind their southern counterparts. Doctors find that they are completely unqualified to work in the South and end up as janitors. Some of them are stuck with the communist mentality and don't work very hard. This then causes their South Korean employers to paint all North Koreans with the "lazy" brush and it continues the cycle. North Korean defectors are generally paid less and treated very poorly so some of them decide to return to the North. Since South Koreans are not allowed to go to the North, they have to defect again, going through a third country. The South Korean government doesn't generally keep track of these things, so the most that can be said is "X number of South Korean citizens are missing". The most recent and available data says that there are less than 1,000 double defectors.