The benchmark Straits Times Index tumbled 28.92 points, or 0.91 per cent, to 3,152.58 on Wednesday - its lowest close since Sept 13.
Some 3.4 billion shares worth $1.4 billion changed hands.
Dealers said investors chose in take profit amid choppy markets, and sentiment was also dampened by Tokyo's 2.2 per cent fall.
Key regional markets mostly fared better than Singapore save Tokyo, with Hong Kong adding 0.55 per cent after reopening from a holiday break. Taiwan gained 0.36 per cent, Australia added 0.17 per cent.