The Stock Exchange of Thailand index dipped on Thursday, while Malaysia shares led the gains, as optimism over a trade deal between the United States and China were renewed following indications of further official talks in Beijing next week.
US Treasury Secretary Steven Mnuchin said on Wednesday that he and other US officials would travel to Beijing to continue trade talks, eyeing a deal before the March 2 deadline.
China is the biggest trading partner of the region.
With easing trade frictions, a dovish Fed and prospects of increased infrastructure spending, foreign investors are now returning to Southeast Asian markets, propelling these markets to record an upward trend for the most part.
So far this year, foreign investors have been net buyers of stocks in markets such as Indonesia, the Philippines, Thailand and Vietnam.
The SET index eased 5.60 points or 0.34% to 1,653.11, in turnover of 50 billion baht. The index was dragged by consumer and health care stocks.
Shares of Bangkok Dusit Medical Services Plc lost 30 satang or 1.27% to 23.30 baht and Siam Makro Plc dropped 1.25 baht or 3.29% to 36.75 baht.
The Malaysian benchmark rose 0.6%, leading gains in the region after thin trading in the region this week due to a two-day closure on account of the Chinese New Year.
Utilities and consumer cyclicals boosted the Malaysian benchmark index, with Tenaga Nasional Bhd and Maxis Bhd climbing 3.7% and 2.5%, respectively.
The Singapore index gained 0.5% to its highest level since Jan 25, helped by telecom and industrial stocks.
"Singapore equities has some catching up to do as the US markets have done well over the last two trading sessions. At the same time, traders are also placing bets ahead of the budget on February 18, 2019," said Liu Jinshu, head of research at Tayrona Financial Pte Ltd.
Shares of Singapore Telecommunications Ltd gained 1% while those of Jardine Matheson Holdings Ltd firmed 1.3%.
The Philippine stock index climbed 0.5%, with gains concentrated in industrial stocks. SM Investments Corp and JG Summit Holdings Inc gained over 2% each.
The Philippine central bank kept its benchmark interest rate steady for a second straight meeting on Thursday, saying inflation risk had fallen on lower crude oil and food prices.
Indonesian stocks also ended the session slightly lower, hurt by consumer and financial stocks. Charoen Pokphand Indonesia Tbk PT slipped 2.8%, while Bank Central Asia Tbk PT slid 0.5%.
Vietnam financial markets remained closed for Chinese New Year holidays.