The 21-year-old belied her modest 50th in the rankings to beat Singapore's world number 13 Yu Meng-Yu 4-2. Her reward is a Wednesday date with China's Ding Ning, the world number two.
Kim is one of 31 athletes representing the reclusive Communist state which has a proud record in the Olympics since making their Summer Games debut in Munich in 1972.
They won a gold in shooting in Germany, one of five medals that year.
North Korea joined the Soviet boycott of the 1984 Los Angeles Games and declined to take part in the 1988 edition hosted by neighbours, South Korea.
But North Korea left London four years ago with a four-gold harvest, including three in weightlifting. In Rio they have two silver medals so far, both in weightlifting.