She said in her weekly national address, Yingluck Government Meets the People, Saturday that the government fully realised the volatility in the world economy had led to lower spending in key markets, particularly the European Union and the United States.
It was the premier's first formal address on Thailand's economic situation in recent weeks after having assigned her deputies to talk about the economic situation and other issues on the weekly programme.
Ms Yingluck said Thai exports were under pressure from the global economic crunch, but most countries in the region were also encountering the same situation, as markets overall were shrinking.
While more emerging markets were surfacing, they were not enough to cover the diminished spending in the major markets, she said.
However, she said she believed Thai exports in the second half of the year would be better than in the first six months, but expansion might be lower than for last year and 2011.
The government will work on free trade negotiations and other means to taper off trade barriers to boost exports.
Ms Yingluck said exports in the final six months would be backed up by the weakening baht against the US dollar.
The Thai currency has depreciated to 32 baht to the dollar.
Regarding economic growth overall, the premier said the country was setting a good pace, but conceded that growth "might not be as high as we expected".
This was partly because spending on the government's investment projects was behind schedule.
She stressed that government spending must be accelerated, though the administration's 350-billion-baht water management scheme and the 2-trillion-baht infrastructure schemes were being delayed.
"I affirm that the government is not sitting idly by. The administration will speed up state spending," Ms Yingluck said.
She also claimed that the number of foreign investors who wanted to invest in Thailand had increased as a result of her frequent overseas trips.
The opposition Democrat Party and some senators have criticised Ms Yingluck for spending hundreds of millions of baht in taxpayers' money on foreign jaunts.
They said Ms Yingluck had spent about 300 million baht on 52 foreign trips to 41 countries over the past two years.
Referring to tourism, Ms Yingluck said foreigners still had confidence in Thailand.
The government believes the number of tourist arrivals will increase to more than 22 million this year, she said.
The prime minister also pledged to help small and medium-size enterprises as the sector can assist in bolstering employment and generating revenue.
The National Economic and Social Development Board (NESDB) last month cut its forecast for full-year gross domestic product (GDP) growth to 3.8-4.3% from 4.2-5.2% in May.
It also lowered its export growth estimate to 5% from 7.6%, reflecting weak demand.