But on the Thai island's southeast coast at Ratsada port, bodies are regularly found floating in the water. They are the suspected victims of slavery and rights abuses that still plague Thailand's multi-billion dollar fishing industry, despite reforms recently introduced by the country's military government, according to Human Rights Watch.

In a just-released report, Human Rights Watch documents murders on the high seas, forced drug use and beatings, and says migrants are being trafficked to work on Thai boats, prevented from changing employers, not paid on time and paid less than the minimum wage.

While acknowledging "important improvements" in the way Thai government agencies police the world's largest seafood export industry the report documents multiple cases of physical abuse and violence against workers on boats.

The report says men who are caught attempting to escape the slavery are frequently beaten and sometimes killed while other workers are forced to watch.

One survivor described men having rope tied around their necks while being dragged through the water behind a boat.

Others described incidents including a man being shot dead after swearing at a skipper and a man strangled, then drowned, because the skipper blamed him for net malfunction.

Wai Phyo Naing, a worker from Myanmar, said the only way he got through 22-hour workdays was the "free coffee" given to the fishermen which he believes contained amphetamines.

"Over time, systems of control based violence and murder achieve a penetrating, almost mythological power that immobilises the will to resist or escape," the report says.

Thailand's government introduced reforms to clean-up the country's US$6.5 billion seafood fishing industry after earlier revelations about abuses that prompted the European Union to warn it could face a ban on its seafood.

The US has also placed Thailand on its "Tier 2" watch list, just one rung up from the worst rating, in its latest trafficking in persons report.

In the past several years Thailand's major seafood companies have been credited with trying to free their supply chains of crews trafficked from neighbouring countries such as Cambodia, Laos and Myanmar.

Seafood sellers in many Western countries, including Australia, have also declared they would not buy seafood from Thai suppliers taking product from boats where abuses occur.

But Human Rights Watch said research carried out in Thailand's major fishing ports between 2015 and 2017 found widespread shortcomings in the implementation of new government regulations and resistance in the fishing industry.

Brad Adams, Asia director at Human Rights Watch, urged Western governments to pressure Thailand to ensure reforms are not window-dressing.

"No one should be fooled by regulations that look good on paper but are not properly enforced," he said.

"International buyers and retailers of Thai seafood have a key role in ensuring that forced labour and other abuses come to an end."

The report said more than 500,000 recent inspections of fishers implausibly did not find a single case of violation of laws or regulations in the industry.

Adisorn Promthep, Director General of the Thai government's Fishery Department, said inspections of the country's commercial fishing boats follow "strict procedures."

But he said thin resources made it impossible to check all of around 11,000 boats. Those with a large number of crew members, or those where there has previously had labour issues, are given priority, he said.

Mongkol Sukcharaoenkana, a representative of Thailand's National Fisheries Association, said the industry had used illegal labour "in the past" but no longer did.

"Everything is fine. Every problem has been fixed by the current government."