Thailand's headline consumer price index (CPI) dropped 0.54% in March from a year earlier, the weakest in 51 months, but slightly better than expectations, commerce ministry data showed on Tuesday.
The reading compared with a forecast decline of 0.60% in a Reuters poll, and with February's rise of 0.74%.
The central bank predicts the headline inflation rate will be minus 1.0% this year, compared with its target range of 1-3%.
The annual core inflation rate was 0.54% in March, compared with a forecast of 0.50%, and February's 0.58%.