Gainers outnumbered losers 161 to 117 while 141 stocks were unchanged with 1.8 billion shares worth 10.5 billion baht (254.6 million dollars) traded.
The Thai baht was stable, supported by technical factors against the dollar to close at 41.17-24 baht to one dollar compared to Tuesday's close of 41.20-22.
The Thai unit closed against the euro at 48.35-69 baht to one euro compared to previous day's close of 48.30-35.
"The market was really in sluggish trading throughout the day, but last-minute buying pushed the index up slightly, but it was not significant," a Bualuang Securities analyst said.
He said the market was now focused on a court hearing that will determine whether the Electricity Generating Authority of Thailand can proceed with its initial public offering.
"It really depends on the court ruling. If the court's verdict allows the listing to go ahead and EGAT's shares start selling, it would give momentum to the market," he said.
Bangkok Bank shed 2.00 baht to close at 100.00 baht, and Kasikornbank lost 0.50 at 63.00 baht, but Siam Commercial Bank added 0.25 at 49.75.
PTT Plc was unchanged at 224.00 but its subsidiary PTT Exploration and Production gained 4.00 at 436.00.
Siam Cement stayed put at 230.00 as well as Thai Airways International at 39.75.
Despite posted huge jump in third quarter profit CPF shed 0.10 to finish at 5.35 baht.