Exports could contract by as much as 3.5% this year if their performance in the remaining six months fetches no more than US$18.7 billion a month on average, say exporters.
After the latest export figures released by the Thai National Shippers' Council (TNSC), chairman Nopporn Thepsithar said shipments could hope for no better than a 2% contraction.
"We're seeing that the worst-case scenario of Thai exports contracting by 3.5% remains possible, as the performance in many major markets — Asean, Japan, South Korea, the EU, Africa, India, the Commonwealth of Independent States — were all in the red in May," he said.
Mr Nopporn said despite exports to the US recovering, close monitoring was still needed to determine how solid that rebound is.
He also urged the authorities to monitor the US Generalized System of Preferences (GSP) closely. If the US cuts Thailand from the GSP as Europe did, exports are likely to encounter more trouble, particularly gems and jewellery, which have expanded significantly in recent years.
The Commerce Ministry last week reported exports tumbled for a fifth straight month in May, down by 5% year-on-year to US$18.4 billion, leading the five-month performance to fall by 4.2% year-on-year to $88.7 billion.
Despite the decline, the ministry is maintaining its full-year export growth forecast at 1.2%, anticipating a better performance in the second half.
"We're more pessimistic than the Commerce Ministry, given the myriad risks and negative factors posing a threat to shipments," he said.
"We expect flat growth in the second half after a 4% contraction in the first half."
Mr Nopporn suggested the government speed up improving Thailand's competitiveness, waive customs-related tariffs levied on both imports and exports and focus more on upgrading Thai products not only in terms of quality but also environmental friendliness and food safety.
He also urged the government to rev up trade talks with potential partners and strengthen intellectual property.
TNSC vice-chairman Vallop Vitanakorn said global uncertainty would almost certainly see June shipments decline by 5-6%.
He urged exporters to hedge against foreign exchange risk to shield the baht from the drama unfolding in Greece.
"The debt crisis has weakened the euro, so exporters must be wary," Mr Vallop said.