The Stock Exchange of Thailand index dropped for a second session in three, while Indonesian shares jumped on Monday after data showed Southeast Asia's largest economy grew the fastest in more than four years in April-June.
The SET index lost 15.85 points or 0.93% to 1,696.24, in turnover of 52 billion baht. The market dropped for a second session in three.
Indorama Ventures Plc and Bangkok Dusit Medical Services Plc shedded 5.8% and 3.7% respectively.
Indonesia's economy grew 5.27% from a year earlier in the second quarter, helped by robust consumption during the Muslim fasting month, and beat a Reuters poll projection of 5.16%.
The stronger growth was driven by an increase in private consumption and government expenditure, which boosted purchasing power, said Leo Putra Rinaldy, an economist at Jakarta-based Mandiri Sekuritas.
"The (GDP) number will provide some relief for both the central bank and the government that has been overseeing rate hikes amid a pressured rupiah and had hiked a cumulative 100bps since May 2018," OCBC Bank said in a note.
The Jakarta SE Composite Index rose to a two-month closing high in heavy trade, led by financials and telecoms.
Telekom Indonesia ended 5.5% higher, while Astra International rose 4.2%.
Among other Southeast Asian stock markets that gained, Singapore rose 0.6% with financials at the helm.
Oversea-Chinese Banking Corp advanced 2% after the lender beat market expectations with a 16% rise in quarterly profit.
Philippine shares closed little changed after declining to a more than two-month low, with losses in industrials and telecommunications outweighing gains in real estate stocks.
SM Investments Corp closed 0.7% lower, while Ayala Land rose 3.6%.
Local investors now await July inflation data ahead of a central bank meeting on Thursday.
The annual inflation likely quickened for a seventh straight month in July due to higher food, fuel and utility costs, according to a Reuters poll.
Asian shares pared gains as Chinese stocks swung into negative territory, dragged lower by the escalating Sino-US trade war.