Thai fishermen catch freshwater white tilapia fish at a fish farm in Samut Prakarn province June 6, 2012. REUTERS/Sukree Sukplang BANGKOK, Thailand — Their condition recalls dark tales from the 18th century: underfed men lorded over by seafaring captains who pay them nothing and maim the disobedient.

Yet these forced labor abuses play out on Thai-owned fishing trawlers each day. And the victims — typically destitute men from Myanmar or Cambodia lured by coyotes full of false promises — continue to wash ashore with accounts of torture and casual homicide.

For years, US officials have urged Thailand, one of America’s closest Asian allies, to rid its $7.3 billion fisheries export industry of these abuses. Though carried out on lawless seas, these crimes risk entangling supermarkets in America, where one in six pounds of seafood is imported from Thailand.

So far, these persistent abuses have hurt Thailand’s reputation but little else. That may change: if one more year passes without major strikes against Thai trafficking syndicates, the US State Department will be forced, by law, to hit Thailand with sanctions.

For four years running, a US State Department annual “Trafficking in Persons” report has labeled Thailand with its next-to-worst ranking. This year’s report, released this week, painted a similarly bleak portrait of Thailand’s efforts to fix what the report called “pervasive trafficking-related corruption.”

Thanks to a pardon from Secretary of State John Kerry, Thailand narrowly dodged the worst ranking, a low rung occupied by Sudan and North Korea, among others. Getting dropped to the lowest rank comes with mandated “targeted sanctions” that cut “non-humanitarian, non-trade-related foreign assistance.”

But after this year’s reprieve, according to US law, Thailand is out of pardons. This means that, to stave off US sanctions, it must finally execute enough raids and arrests in the next 12 months to prove its sincerity in attacking traffickers. (Thailand’s Ministry of Foreign Affairs, reached by GlobalPost, declined to respond to the latest report.)

Thailand’s efforts so far amount to “an engine that doesn’t catch,” said Ambassador-at-Large Luis CdeBaca, who heads a special US anti-trafficking office. “The notion of the Thai fishing fleet has been something that we’ve been raising more and more as we’ve come to realize that there is just so much abuse out on those boats.”

In the 2012 GlobalPost investigation “Seafood Slavery,” former captives who’d escaped Thai trawlers described 18-hour days for zero pay on unregistered “ghost boats.” Most had witnessed fellow fishermen stabbed, crippled or tossed into the sea. Traffickers confided that captives — or boys as young as 16 — can be purchased for roughly $600. They are forced to toil for years without payment.

Said one Thai crewman: “Years ago, I saw an entire foreign crew shot dead ... The boss didn’t want to pay up, so he lined them up on the side of the boat and shot them one by one.”

Such cruelty persists because it takes place in an oceanic abyss, often in international waters. Slave-caught seafood is typically transferred to what Thai captains call a “Mae Rua” — mothership — where sardines, mackerel and varied catch from scores of different boats are absorbed into expansive ice rooms.

The supply chain is further muddled through a system of onshore brokers, which purchase fish from motherships before selling tubs of seafood to processing plants that prepare packages for export.

Dealing a serious blow to networks of human smugglers and criminal fishing syndicates within the next year could prove to be a massive undertaking. In recent years, the Thai government has taken minor steps: increasing police training, upping potential sentences for trafficking crimes and constructing more shelters for escapees.

But anti-trafficking workers on the front lines contend that this has had little impact.

“It feels pretty much the same. We’re still fighting the same battles,” said a United Nations source who is not authorized to speak to the press. “So far, there just hasn’t been much of an impact on these brokers or the exploitative businesses that are benefiting from that labor.”