Thai and Philippine shares slumped over 1.5% each on Thursday, in line with broader Asia, a day before China and the United States were set to hit one another with punitive tariffs that risked triggering a full-scale trade war.
The Stock Exchange of Thailnd Index snapped three straight sessions of gains in very thin trade. The index plunged 27.78 points or 1.71% to end the day at 1,601.42. Only 13.8 million shares changed hands, compared with the 30-day average of 13.4 billion shares.
Almost all the sectors ended in red. Energy and utility stocks were the top losers with PTT Plc shedding 3.1%, while Indorama Ventures Plc slid 5.3%. The biggest loser was Beauty Community Plc. Its shares nosedived 20% to 7.20 baht.
Oil declined after US President Donald Trump demanded Opec cut crude prices, although the market found some support from an Iranian threat to block shipments through the Strait of Hormuz.
Philippine stocks fell for the first time in five sessions after data showed June inflation rate quickened to a five-year high.
The Philippine consumer price index stood at 5.2% in June, above the 4.8% forecast in a Reuters poll, raising expectations of a third interest rate hike this year.
"Inflation data is negative for equity markets and it could (trigger) more rate hikes, which might result in slower growth going forward," said Charles William Ang, associate analyst at COL Financial Group.
Blue chips SM Investments Corp and Metropolitan Bank and Trust Co fell 3.8% each.
Vietnam shares fell for a third session in four and closed 1.7% lower as financials weighed.
JSC Bank for Foreign Trade of Vietnam (Vietcombank) fell over 6% while Petrovietnam Gas JSC was down about 7%.
Meanwhile, Malaysian shares closed slightly higher after trading in red for most part of the session.
Annual export growth in May slowed sharply from the previous month amid lower demand for palm oil, data showed.
Malaysia's palm oil inventories are forecast to have dropped to a nine-month low in June as production in the world's second largest producer fell faster than exports, according to a Reuters survey.
Indonesian shares also recovered from early falls to close marginally stronger, supported by energy and telecom stocks.
Telekomunikasi Indonesia gained nearly 2%, while United Tractors rose 3.6%.
Singapore shares extended gains into a second session, helped by telecom stocks.