While nearly all Thai factories are back in production, the global slowdown has kept them working at well less than capacity. In July, manufacturing production was down 5.82 percent from a year earlier.
The flooding hit seven big industrial estates from October, severely hurting car and electronics plants.
Thailand is a regional hub and export base for the world's top car producers and the world's number two producer of hard disk drives.
The auto sector is now back to normal but some other firms have yet to reopen, the Industry Ministry says.
"The export growth data is likely to remain lackluster, still weighed down by the rather bleak global demand, especially in electronics and other consumer-oriented manufacturing goods," said Gundy Cahyadi, an economist at OCBC Bank in Singapore.
Exports account for more than 60 percent of Thailand's gross domestic product. Industrial goods usually account for 65 percent of shipments and commodity products 17-19 percent.
Other trade-reliant Asian economies such as South Korea and Taiwan have also reported falling shipments due to sputtering demand across much of the world.
In the first seven months of 2012, Thai shipments in dollar terms were down 0.4 percent from a year earlier. Even though flooding battered the economy in the last quarter, exports for all of 2011 rose a revised 14 percent from the year before, according to Commerce Ministry data.
Bank of Thailand Governor Prasarn Trairatvorakul told Reuters last week the slowdown in global demand would cut export growth this year to a figure lower than the official scaled-down forecast of 7 percent. But he said he remained confident the central bank's target for Thai economic growth this year of 5.7 percent can be achieved.
A senior Commerce Ministry official said last month exports were likely to grow 9 percent this year, rather than an earlier government target of 15 percent.
According to the Reuters poll, imports in August had their first year-on-year fall since January.
They were seen to be down nearly 6 percent. Economists projected the fall due to fading demand for restocking and re-equipping for factories, as well as last year's high base figure.
A fall in imports does not augur well for exports, as many imported materials go into products that are then exported.
The Bank of Thailand left its benchmark interest rate steady at 3 percent earlier this month for the fifth straight meeting, though two of the five policy committee members present voted for a cut due to the worsening global growth picture.
But the central bank has said it is ready to adjust the rate to help the economy if needed. Most economists expect monetary policy to be on hold for the rest of the year, barring an economic slump.