In the morning session, Krungsri Securities forecast the index on Tuesday would fluctuate between 1,640 and 1,660 points despite reports that the government may suspend the emergency decree as domestic Covid-19 infections continue to decline.
It added that the index also gained positive sentiment after the Federation of Thai Capital Market Organisations reported that the investor confidence index had soared 124.3 per cent to 144.37 points.
However, it advised investors to beware of mass sell-offs of shares in response to signs of overbought stocks and foreign fund outflows.
The 10 stocks with the highest trade value today were GULF, ADVANC, CPALL, KBANK, PTT, SCGP, INTUCH, BANPU, CBG and THCOM.
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Other Asian indices were mixed:
Japan's Nikkei Index closed at 29,916.14, up 256.25 points or 0.86 per cent.
China's Shanghai SE Composite Index closed at 3,676.59, up 54.73 points or 1.51 per cent, while the Shenzhen SE Component Index closed at 14,702.90, up 156.29 points or 1.07 per cent.
Hong Kong's Hang Seng Index closed at 26,353.63, up 190.00 points or 0.73 per cent.
South Korea's KOSPI Index closed at 3,187.42, down 15.91 points or 0.50 per cent.
Taiwan's TAIEX Index closed at 17,428.87, down 66.43 points or 0.38 per cent.