Their net sell hit Bt2.44 billion on Monday, expanding the month-to-date net sell to Bt35 billion.
Their year-to-date net sell has reached Bt188.39 billion.
The Stock Exchange of Thailand today lost another 12.73 points or 0.95 per cent, to 1,328.40 points, on very thin turnover of Bt23 billion.
Other Asian bourses also fell for a fourth day, as investors awaited a Federal Reserve meeting starting tomorrow to gauge the timing of stimulus cuts.