The Bank of Thailand has grown more pessimistic about the prospects of achieving its export growth forecast of 9% this year as the intensifying trade dispute between the world's top economies dampens global demand.
Export value contraction in September was beyond the central bank's current forecast and full-year growth could be slower than projected, said Pornpen Sodsrichai, director of economic analysis at the Bank of Thailand.
October's reading will provide clarity, she said.
"The [central bank] estimates export growth for this year at 9%, while it grew 8.1% for the first nine months of the year," Ms Pornpen said. "To achieve the forecast, exports need to grow 11.4%, which is considered a challenging figure, for the final quarter."
Given the high-base effect, year-on-year export growth in October likely declined from September's level.
Payment-based exports dipped 5.5% year-on-year in September on a mix of negative factors, including the US-China retaliatory tariffs and a high comparative base.
The overall contraction was also attributed to accelerated exports of cars to Australia in earlier periods and the temporary disruption of goods transport to trading partners, particularly Japan, the Philippines and Hong Kong, due to natural disasters.
Moreover, the high-base effect stemming from last year's surge in exports of mobile phones from the launch of new models, plus accelerated shipment of solar cells and washing machines before the US safeguard measures were put in place, weakened exports.
In September, Thailand's overall shipments to China contracted 14.1% from a year earlier.
Another key engine driving the Thai economy, tourism, also tapered off in September, with foreign arrivals registering moderate growth of 2.1% year-on-year.
Foreign tourist growth declined to 1.9% in the September quarter from 8.4% and 15.5% in the second and first quarters, respectively, due to a decline in Chinese arrivals.
With the slower growth pace of foreign arrivals and the export contraction, the economy in September expanded at a slower pace from the previous month.
Positive momentum in September was supported by domestic demand from both private consumption and investment, as well as public spending.
Ms Pornpen said the central bank will monitor economic momentum for the rest of the year.