Economists in a Reuters poll had forecast quarterly growth of 2.3 percent in October-December, and an annual pace of 2.4 percent.
The full-year growth was the weakest since flood-hit 2011. In 2013, there was 2.9 percent expansion.
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Thailand is the last major Southeast Asian economy to report 2014 growth, and had by far the weakest. Malaysia last week reported higher-than-expected four-quarter and 2014 growth.
For months prior to the coup, Thailand suffered virtual paralysis in policy-making amid political tensions. The junta has struggled to lift growth as exports remain weak, consumption is still subdued and government spending slow.
The October-December performance was the best for any quarter for last year, but reflects a low base from late 2013, when anti-government protests began. Badly-hit tourism is recovering slowly.
The agency revised economic on-quarter growth in July-September to 1.2 percent, from 1.1 percent stated earlier.
The central bank, which has kept its policy interest rate at 2.0 percent for nearly a year, next meets on March 11.
The National Economic and Social Development Board (NESDB) on Monday kept unchanged its 2015 growth forecast of 3.5-4.5 percent. It cut its export growth projection to 3.5 percent from 4.0 percent.