Thai share prices closed 0.20 percent lower on Monday on the back of profit-taking and a decline in energy-linked stocks brought on by weaker oil prices, dealers said.
They said that the fall came after the market saw a gain of nearly two percent last week, with foreign investors rallying behind energy companies in response to record global oil prices.
The Stock Exchange of Thailand (SET) composite index fell 1.52 points to 771.54 and the blue chip SET 50 index declined 1.66 points to 538.91.
Losers outnumbered gainers 235 to 124, with 89 stocks unchanged on turnover of 2.7 billion shares worth 17.1 billion baht (455 million dollars).
The Thai baht traded at a six-year high against the dollar, closing at 37.58-63 to the greenback Monday, up from Friday's 37.77-80.
The Thai currency was at 46.45-65 to the euro, little changed from 46.60-66.
"The Thai index slipped slightly in line with other regional stocks as oil prices are likely to rise further with continued conflicts between the United States and Iran," said Ronnakit Sarinwong, vice president of Adkinson Securities.
"Energy-related stocks are the only factor that pressured the stock market today," he told AFP.
Although the index fell again Monday, dealers said it was still at a two-year high.
Crude oil prices eased Monday after spiking to an all-time high of 75 dollars in New York and 74 dollars in London on Friday amid rising tensions over Iran's controversial nuclear program and tight US gasoline supplies.
Shares in Thailand's top energy firm PTT gained 2.00 to 268.00 baht, and its subsidiary PTT Exploration and Production rose 5.40 to 135.00.
Thai Oil, the country's largest oil refinery by capacity, edged up 0.50 to 72.00.
Top lender Bangkok Bank lost 2.00 to 114.00. The third-largest lender, Kasikorn Bank, also slumped slightly by 1.00 to 65.50.
Thai Airways International was down 0.75 to 45.75.