Inflation as measured by the headline consumer price index (CPI) rose 0.62% in June from a year earlier, after the previous month's annual increase of 1.54%, the Commerce Ministry said on Friday.
Last month's figure compared with a forecast increase of 1.12% in a Reuters poll, and against the Bank of Thailand's (BoT) target range of 1% to 3%.
The core CPI, which excludes volatile food and energy prices, was up 0.36% on the year in June.
Fresh food prices slowed in June because of favourable weather, while other goods prices had a limited impact on inflation, the ministry said in a statement.
The annual headline inflation rate in the third quarter is expected to be close to the second quarter's 0.78% pace, Poonpong Naiyanapakorn, the director of the trade policy and strategy office, told a press conference.
Headline inflation is expected to be more than 1% in the fourth quarter, he added.
Current inflation remains appropriate for the economy, he said.
"It is stable and predictable for both business operators and households to make plans," he added.
In May, the headline CPI rose 1.54% from a year earlier, returning to the central bank's target range of 1% to 3% for the first time in a year.
In the first six months of 2024, average annual headline inflation was 0.0%, with the core rate at 0.41%.
The ministry retained its headline inflation forecast for the year of between 0% to 1%.
The BoT has said it expects headline inflation to be below the target range in the third quarter before returning to the range in the fourth quarter.It has been keeping interest rates at decade highs despite intense government pressure to reduce borrowing costs to boost economic growth.