Thailand's planning agency slashed its forecast for economic growth this year to 3.0 to 4.0 percent from 4 to 5 percent seen in November due mainly to a delay in public investment projects and weak private consumption.
In 2013, the economy grew 2.9 percent, far slower than the previous year's 2012 as exports were tepid and political tensions hurt domestic demand and tourism.
The National Economic and Social Development Board, which compiles gross domestic product (GDP) data, also cut its 2014 export growth forecast to 5 to 7 percent from 7 percent seen earlier.
It expects headline inflation this year to be 1.9 to 2.9 percent, compared with 2.1 to 3.1 percent seen previously.
The Bank of Thailand last month cut its forecast for 2014 GDP growth from 4 percent to around 3 percent but recently said it could be even lower.
Economists in a Reuters poll last week forecast 2014 economic growth at 3.0 percent.