The stock market fluctuations come amid US President Donald Trump's visit to China.
South Korea's Kospi rose about 1.4 percent shortly after the open, hitting a record. A few hours later, the index was down 3.0 percent, coinciding with another plunge in oil prices.
Trading on the Tokyo Stock Exchange followed a similar pattern during the day. The Nikkei 225 opened higher but was down 1.3 percent by lunchtime. The broader Topix was down 0.4 percent.
In China, the stock markets were clearly down at the open and were rising by lunch. Shanghai rose 0.2 percent, Shenzhen rose 0.4 percent.
Hong Kong's Hang Seng was down 0.9 percent.
