Thailand's manufacturing production index (MPI) in February unexpectedly dropped 1.6% from a year earlier, led by lower production of steel, computers and rubber products, the Industry Ministry said on Tuesday.
That compares with a forecast rise of 0.52% in a Reuters poll, and against January's 0.18% increase.
Capacity utilisation was at 69% in February, down from January's 70.49%.
The ministry has forecast the MPI will increase between 2% and 3% this year, after 2018's 2.8% rise.