The 2008 incident was the deadliest in a wave of tragedies afflicting migrants making perilous journeys from impoverished Myanmar in search of work in neighbouring Thailand, where they often end up exploited and abused.
The victims were among 121 people crammed into the six metres (20 feet) by 2.2 metres container with a broken ventilation system for the journey to the resort island of Phuket to work as day labourers.
Four Thais were convicted on Thursday of gross negligence resulting in death and of breaking immigration laws, an official from a court in the country's southern Ranong province said.
The owner of the container truck was sentenced to 10 years in prison, a second defendant received nine years and a third - who owned a jetty in southern Thailand where the migrants arrived by boat - was jailed for six years.
A woman defendant had her sentence halved to three years after confessing, the official said.
“Three of them were granted bail of between $13,000 and $6,500 while they file appeals,” the official said, adding that one defendant had been held in custody after failing to meet bail terms.
The truck driver, who fled the scene after discovering the tragedy, was jailed for six years in August 2008 having admitted to his role in the crime, the official added.
Survivors have recounted desperately trying to raise the alarm as they fought for breath in the storage box.
“No matter how many times we hit the container the driver did not pay any attention,” one female migrant who was on board told Thai television.
More than two million migrant workers are registered to work in Thailand, most of them from Myanmar, labour ministry figures show, but as many as one million undocumented workers are believed to be in the kingdom.
Thailand this week extended a deadline by three months for unregistered migrants to gain a work permit or face deportation.
Huge numbers of people from Cambodia, Laos and Myanmar work illegally in low-paid jobs in construction, seafood processing and clothing factories, where a lack of legal status leaves them vulnerable to exploitation.