The month's $2.87 billion trade deficit marks an improvement on March's $4.59 billion figure, according to the Ministry of Commerce, which said exports were dragged by European economic woes that have dampened global demand.
Exports fell 3.67 percent in April compared to a year earlier to $16.91 billion, from a 6.54 percent slump in March.
Imports grew 7.87 percent to $19.79 in the month, from an increase of 25.62 percent the previous month.
Deputy Commerce Minister Poom Sarapol reiterated an export growth target of 15 percent for 2012, with "good signs" of growth within the ten-member Association of Southeast Asian Nations (ASEAN) bloc and China.
The rise in imports was partly driven by the procurement of machinery to fix or replace equipment damaged by several months of floods, he added.
Thailand posted double-digit economic growth in the first quarter of 2012 as it recovered from the fallout of widespread flooding that left more than 800 people dead and disrupted production in the country's industrial heartland.
At their height the floods affected 65 of the country's 77 provinces, deluged hundreds of thousands of homes and forced the closure of large industrial parks, disrupting global supply chains.
Manufacturers are getting their factories back up and running and the National Economic and Social Development Board (NESDB) economic planning agency has forecast economic growth of 5.5-6.5 percent for the whole of 2012.
Exports fell 3.86 percent to $71.56 billion in the first four months of 2012, while imports rose 9.79 percent to $79.61, resulting in a trade deficit of $8.05 billion.
-- Dow Jones Newswires contributed to this story --