BANGKOK (Reuters) - Thailand's economy contracted 2.1 per cent in the first three months from the previous quarter and 0.6 per cent from a year earlier as exports were soft and prolonged political unrest has battered domestic demand and tourism.

A Reuters poll of economists had forecast a quarter-on-quarter contraction of 1.6 per cent in January-March, and year-on-year growth of 0.1 per cent.

The National Economic and Social Development Board, which compiles the data, revised quarter-on-quarter GDP in October-December 2013 to 0.1 per cent growth from 0.6 per cent growth stated earlier.

It left year-on-year growth for the last quarter of 2013 at 0.6 per cent.

Thailand's planning agency also cut its forecast for economic growth this year to 1.5-2.5 per cent from 3.0-4.0 per cent seen in February, due to weak exports and faltering domestic demand hurt by months of political unrest in Bangkok.

For the whole of 2013, the economy expanded 2.9 per cent, slowing from the previous year.

The National Economic and Social Development Board, which compiles gross domestic product (GDP) data, also lowered its 2014 export growth estimate to 3.7 per cent from 5.0-7.0 per cent seen earlier.

It expects headline inflation this year to be 1.9-2.9 per cent, unchanged from the previous estimate.

The Bank of Thailand said its recent scaled-down GDP growth estimate of 2.7 per cent would be cut further next month.

Economists in a Reuters poll last week forecast 2014 economic growth at 2.0 per cent.