About 90 were injured as anti-government protesters clashed with police guarding the stadium where political parties drew their poll numbers in the morning.
The index ended the day at 1,308.46 points, on turnover of Bt26 billion. In the past three months, the index has lost 6 per cent. Year to date, the index lost 4.27 per cent.
Foreigners' net sell of Thai shares on Thursday totalled Bt2.5 billion. Foreign investors have been net-sellers of Thai shares throughout December, with accumulated net sales of Bt39.9 billion.
The year-to-date net sales reached Bt193.19 billion.
Political concerns also pressured the dollar/baht exchange rate. The baht ended at 32.82 per dollar from 32.74 yesterday.