Inflation rose to 4.29 percent in August year-on-year, up from 4.08 percent in July, according to the Commerce Ministry.

Month-on-month prices gained 0.43 percent in August, led by the food and energy sectors.

Thailand's central bank last week raised its key interest rate for the sixth time this year, to 3.50 percent -- the highest level in about three years -- saying inflation was a bigger threat than slowing global economic growth.

Thailand has lifted its key lending rate by 225 basis points since July 2010 in an attempt to tame inflation.

The Bank of Thailand has warned that the new government's populist policies, such as a higher minimum wage and increased rice prices for farmers, are likely to fuel cost pressures.

At the same time Yanyong Phuangrach, permanent secretary at the Commerce Ministry, said inflation was expected to ease back below four percent in September because of falling oil prices.

The ministry expects an inflation rate of between 3.2 and 3.7 percent for the whole of 2011.

Government data showed last week that the Thai economy contracted 0.2 percent in the second quarter as supply shortages caused by Japan's massive earthquake led to a sharp slowdown in exports.