The use of free trade agreement (FTA) privileges and the Generalised System of Preferences (GSP) by Thai exporters dropped by 2.95% in the first 10 months of the year to US$60.3 billion.
Keerati Rushchano, the department's director-general, said lower values were in line with the overall export outlook, which was marred by weak global demand, ongoing trade wars and the strong baht.
Of the total value, FTA privilege use contributed $55.9 billion, down by 4.30% year-on-year from the first 10 months, with shipments under the GSP making up $4.43 billion, a surge of 18.1% from last year.
Mr Keerati said despite a fall in the overall FTA privilege utilisation, higher utilisation was seen in potential markets like Peru, China and Japan.
The top five export markets with the highest use of FTA privileges were Asean, China, Australia, Japan and India.
The Thai-Asean FTA continued to see the highest volume, totalling $20.8 billion during the first 10 months, with the Thai-China FTA tallying $15.3 billion, while Thai-Australia privileges were $6.74 billion.
The values for Thai-Japan and Thai-India FTAs totalled $6.34 billion and $3.65 billion, respectively.
The top five items that used FTA privileges were trucks; fresh durian; natural rubber mixed with synthetic rubber products; fruits such as guava, mango, and fresh and dried mangosteen; and sugar from sugar cane.
Thailand has 12 FTAs in place, excluding the Asean-Hong Kong FTA that took effect on June 11 this year.
Mr Keerati said the US retained the highest rate of GSP utilisation, making up $4.02 billion, followed by Switzerland at $262 million, Russia at $119 million and Norway at $19.7 million.
The GSP is used for trade with the US, Switzerland, Russia and Norway. Japan removed preferential tariffs on Thai products on March 31.