Thailand's manufacturing production index dropped 0.36% in April from a year earlier, missing analysts' forecasts.
The April reading compared with a 0.2% increase forecast in a Reuters poll, following a revised 1.30% rise the previous month.
The industry ministry sees full-year factory output up 1.0% to 2.0%, lower than the earlier 1.5% to 2.5% range.
The ministry attributed the decline to the impact of the war in the Middle East and higher costs pressuring profits.
Tourism, a key economic driver, also weakened, affecting related industries.
First quarter output grew 0.94% annually. The outlook for May is higher on a month-on-month basis.
