* Q2 GDP +2.3% y/y vs +2.4% in Reuters poll and +2.8% in Q1
* Planning body cuts 2019 growth f'cast to 2.7-3.2% from3.3%-3.8%
* Changes 2019 export forecast to -1.2% from +2.2%
* A stimulus package unlikely to have solid impact -economist(Adds details, economist comment)
By Orathai Sriring and Kitiphong Thaichareon
BANGKOK, Aug 19 (Reuters) - Thailand's economy expanded atits slowest pace in nearly five years in the second quarter astraditional growth drivers sputtered, which led the governmentto significantly cut its forecast for full-year expansion.
The state planning agency, reporting April-June data onMonday, reduced its forecast for 2019 growth to 2.7-3.2%, versus3.3%-3.8% seen in May. It also sharply changed its estimate forthis year's exports, now seeing 1.2% shrinkage instead of 2.2%growth.
The downwardly-revised forecasts for 2019 come at a time ofrising global trade tensions and as Thai exporters fret aboutstrength of the baht, which has gained more against thedollar than any other Asia currency this year.
Trade-reliant Thailand, the region's second-largesteconomy, reported second-quarter growth of 2.3% from a yearearlier.
That was just below the 2.4% seen in a Reuters poll andwell down from the 2.8% pace for January-March.
On a quarterly basis, growth was a seasonally adjusted 0.6%,weaker than the poll's 0.7% forecast and the January-March's1.0%.
Capital Economics said it expects the economy to remainweak, projecting 2019 growth of 2.5% and then 3.0% next it year.
Charnon Boonnuch of Nomura said he expects second halfgrowth to rise to 3.4% from 2.6% in the first, helped by fiscaland monetary policy easing.
All Southeast Asian economies except Malaysia have reportedslower annual growth in the second quarter than the first, hurtby the U.S.- China trade war and cooling global demand.
Thailand's exports contracted 4.2% in the second quarterfrom a year earlier. In 2018, they rose 7.5%.
The planning agency said economic growth should be firmer inthe second half than the first, boosted by government stimulusmeasures.
PLANNED PACKAGE
Thailand is planning a $10 billion stimulus package in a bidto get GDP growth of at least 3% this year, and 3.5% next year,according to Finance Minister Uttama Savanayana.
But as the Thai economy is increasingly reliant on externaldemand, it's hard for such policies and measures "to truly makea significant impact on the slowing economy," said KobsidthiSilpachai, head of capital markets research of Kasikornbank.
The April-June growth pace was affected by smaller gainsfrom tourism and domestic consumption as high household debtrestrained consumer spending.
In April-June, private consumption rose 4.4% from a yearearlier and private investment rose 2.2%, while publicconsumption rose 1.1%, crimped by the delayed formation of agovernment after March's elections, planning agency data showed
Annual growth in foreign tourist numbers slowed to 1.1% inthe June quarter from the previous period's 1.8%.
Given increased risks to growth, benign inflation and thestrong baht, most economists expect the central bank to cut itskey interest rate later this year after a surpriseeasing on Aug. 7. The next policy review is Sept. 25.
($1 = 30.90 baht)
(Editing by Richard Borsuk)