Thai stocks fell 0.77 percent on Tuesday after three days of gains as profit taking hit recent risers like communications and brokerages after a computer problem wiped out morning trade, analysts said.
The benchmark Stock Exchange of Thailand composite index closed down 5.25 points at 673.88 after rising 6.6 percent over the previous three trading days.
The big-cap SET 50 dropped 0.74 percent to 47.15 points and turnover was 18.4 billion baht ($445 million), down from 30.3 billion baht on Monday.
The communications sub index fell 2.68 percent, dragged lower by a 5.5 percent fall of shares in mobile phone firm Advanced Info Service to 104 baht after they had risen almost three percent on Monday.
Brokerage stocks were mostly lower as investors sold shares after the trading delay soured sentiment on the sector.
The finance and brokerage sub index fell 0.8 percent as shares in Seamico Securities fell 1.1 percent to nine baht.
"The delay in the market opening did dampen sentiment on the sector. But it was just a brief negative reaction, in my view," said Amarej Singnarong, head of research at Adkinson Securities.
"I think foreign and institutional investors remain bullish on Thai stocks and I expect their buying to support the market," he said.
Amarej said he expected resistance on the main index on Wednesday at 700 points and support at 671 points.