Thailand's fishing industry is concerned at a U.S. move to end duty-free status of many Thai exports, including seafood. The Thai government is seeking talks on the U.S. decision, which some claim could be the start of a U.S.-Thai trade dispute.

At the port of Samut Sakhon in central Thailand, wooden fishing boats bring home the day's catch. They are tied up by the fish dock where the cargo is man-handled from below decks.

Buckets of fish are slid down metal-railed gangplanks to the shore, where waiting dock workers sort them by size and species.

Much of the fish is exported to the U.S. where Thai seafood has benefited from zero duty, but now it is one of the 573 products to lose "preferential status."

The U.S. is Thailand's second-largest export market with total shipments worth almost 32 billion U.S. dollars in 2018.

The hike in duty will add costs of at least 1.3 billion dollars, with some say far more.

The withdrawal of Thai goods from the U.S.' Generalized System of Preferences is due to come into effect on April 25, 2020.

The U.S. said it was taking the step due to "longstanding worker rights issues in the seafood and shipping industries in Thailand."

The U.S. wants migrant workers to be able to form trade unions and engage in collective bargaining.

Making the announcement, U.S. President Donald Trump said, "I have determined that Thailand is not taking steps to afford workers internationally recognized rights … it is appropriate to suspend the duty-free treatment."

But a senior Thai fisheries official said the action was unjustified.

"No country in the world allows migrants to form unions because they are temporary workers," said Wicharn Sirichai-Ekawat, former chairman of the National Fisheries Association of Thailand.

"I can say there is no difference between conditions for Thai workers and migrant workers. The U.S. demands are unfair to Thailand."

The timing of the decision is being questioned as it comes just a year after the U.S. upgraded Thailand from Tier 3 to Tier 2 in its annual Trafficking in Persons Report, for tackling worker abuse.

The European Union also lifted a threatened ban on Thai seafood because of improved efforts to regulate the industry.

Many believe the decision is more about protecting the U.S.' commercial interests.

The U.S. has an almost 20 billion dollar trade-deficit with Thailand, something President Trump has said he wants to change.

"It seems our fishing industry is always targeted by many organizations and Western countries, such as the U.S., EU, Australia and New Zealand," said Sirichai-Ekawat. "They use labor issues to suspend Thailand from the GSP (Generalized System of Preferences)."

The move comes shortly after Bangkok banned the use of a number of chemicals in pesticides, which could disrupt U.S. farm exports to Thailand.

There has been speculation that the suspension might have been for retaliation. Both sides have denied this but it has led to concern that it could be the beginning of a wider trade dispute between the U.S. and Thailand.

The Thai government is playing down the impact of the U.S. decision - but it comes at a time when Thai exports are already struggling because of the China-U.S trade war and a record-high for the Thai Baht, which is pushing up the prices of its products overseas.

Thai officials are seeking a meeting with their U.S. counterparts.