The headline consumer price index rose 0.79 percent in March from a year earlier, after February's 0.42 percent increase, commerce ministry data showed on Monday.
A Reuters poll projected a rise of 0.90 percent in March.
In the January-March period, the index rose 0.64 percent from a year earlier.
The Bank of Thailand (BOT) last week trimmed its 2018 headline inflation forecast to 1.0 percent, from 1.1 percent seen earlier, and compared with its target range of 1-4 percent.
The core CPI, which excludes raw food and energy prices, rose 0.63 percent in March from a year earlier, in line with the poll's median. In January-March, the index was up 0.61 percent year-on-year.
State price controls, subsidies and sluggish domestic demand have also held down consumer prices.
The BOT has left its policy interest rate steady at 1.50 percent, near record lows, since April 2015.
At its March 28 meeting, the vote to hold the rate was 6-1, with one dissenting vote for a quarter-point increase.
The BOT will next review policy on May 16. Most analysts expect no policy change for the rest of 2018, though some predict rate increases in the second half of this year.