Taipei, July 30 (CNA) Taiwan shares closed below the 40,000-point threshold on Thursday after a volatile session that saw the benchmark index swing more than 1,700 points, erasing an intraday surge of over 1,100 points as late selling dragged the market lower. The Taiex, the Taiwan Stock Exchange's benchmark index, ended down 105.88 points, or 0.26 percent, at 39,933.30 on turnover of NT$1.10 trillion (US$34.08 billion). Aspeed Technology Inc., the market's most expensive stock, rose NT$295, or 2.29 percent, to NT$13,205, helping lift other high-priced shares. Instead, he expects the market to remain volatile in the near term as it gradually forms a bottom. According to the Taiwan Stock Exchange, foreign institutional investors were net sellers of NT$48.31 billion of shares on the main board Thursday.