At the close, the Stock Exchange of Thailand index lost 64.55 points or 4.73 per cent to 1,301.06 points.
Turnover was Bt60.5 billion.
Other markets also suffered:
Hong Kong down 5.17 per cent to 21,251.57 - its lowest point since May 2014
Philippine down 6.7 per cent
Tokyo down 4.61 per cent to 18,540.68 points, its lowest since February
Australia down 3.9 per cent to a two-year low