Indonesia's trade surplus soared to twice the forecast amount in August as imports such as raw materials and capital goods fell more than expected, government data showed on Friday.

The surplus for Southeast Asia's biggest economy was $3.12 billion, the statistics bureau reported, far above the $1.55 billion median forecast of 19 economists surveyed by Reuters and up sharply from $1.31 billion in July.

Imports fell 14.77% to $18.88 billion, deeper than the 9.33% forecast drop. Crude oil imports sank about 39% from a year earlier, said Amalia Adininggar Widyasanti, acting head of Statistics Indonesia.

The import drop was influenced by seasonal factors, said economist Irman Faiz at Bank Danamon, who maintained his forecast that imports will rise for the rest of the year due to higher oil prices and an increase in manufacturing.

"On the other hand, weakening global growth and lower commodity prices are expected to result in reduced exports," he said, keeping his 2023 current account deficit forecast at 0.4% of gross domestic product.

Indonesia's exports dropped 21.21% in August from a year earlier to $22 billion, compared with a forecast 22% decline, on lower prices for the country's top commodities, such as coal, palm oil and natural gas.

Indonesia's policymakers must remain cautious about currency volatility given expectations of a current account deficit and with U.S. Treasury yields rising, said Trimegah economist Fakhrul Fulvian.

The rupiah fell to its lowest since March on Friday before rebounding. It was trading at 15,363 per dollar at 0354 GMT, barely changed from a day earlier.

(Reporting by Fransiska Nangoy, Stefanno Sulaiman; Editing by Kanupriya Kapoor, Tom Hogue and William Mallard)