Apaporn Sawangpak, vice president at DBS Vickers Securities (Thailand), said that political instability is attributable to the fall, as investors were concerned with the red-shirts' plan to gather on November 10, when protests against the amnesty bill remain.
"It's worrying if the political tensions would intensify, with the protests of several groups," she said.
She noted that if the index falls below 1,400 points next week, it could fall further to 1,380 and 1,350 points.