Asean members are being urged to rely largely on domestic consumption and growth over the next five years now that exports are unlikely to recover over the period due to the slow global economic recovery.
Porametee Vimolsiri, secretary-general of the National Economic and Social Development Board (NESDB), said the world economy is expected to grow by 3.1% next year from an estimated 3% this year, with the performance over the next five years likely to remain flat.
Mr Porametee said shipments of almost all Asean members fell last year, with those of Indonesia falling 14%, Malaysia down 15% and the Philippines down 5%.
Exports fell more than expected in 2015, declining by 5.78%, the biggest drop in six years.
Thailand's exports fell for the third straight year, with export value totalling US$214 billion last year, the biggest decline since the US debt crisis sent exports tumbling 14.3% in 2009.
Shipments fell by 0.3% in 2013 and 0.4% in 2014 against rises of 2.93% in 2012, 15.2% in 2011 and 26.8% in 2010.
Imports totalled $203 billion in 2015, down by 11%, giving Thailand a trade surplus of $11.7 billion.
Vietnam reported shipments grew 8% last year, but the growth rate had eased from the normal two-digit growth, said Mr Porametee.
Exports of almost Asean members are expected to remain bleak this year, because the European Union still faces economic problems, while the global economy remains poor.
The NESDB projected Asean's economy to grow by 4.8% this year, up slightly from 4.7% last year.
Asean enjoyed an average 5% growth over the past eight years.
However, he said Asean still boasts of vast investment opportunities, particularly Cambodia, Laos, Myanmar and Vietnam. Those countries may need direct investment from third countries, he said.
"Thailand's prospects remain promising," he said. "But with the difficult external environment, Thailand sill needs to continue investment over the next five years to propel domestic growth."