Around 850,000 migrant workers in Thailand have met a deadline to start a registration process, the labour ministry said Thursday, as rights groups made renewed calls for a halt to the policy.

Thailand had ordered 1.3 million eligible citizens from neighbouring Burma, Cambodia and Laos to begin the process of registering and verifying their nationality by Sunday or risk deportation.

To enter the process migrants must pay registration and medical fees of 3,800 baht ($US116) – a large sum for people who mostly have low-paid jobs in the manufacturing, agricultural and domestic sectors.

The full registration process takes two years to complete and will eventually entitle the migrants to claim temporary work permits.

“Some 850,000 migrant workers met the deadline” said Supat Gukun, a labour ministry official.

The 1.3 million are eligible because they registered for different one-year work permits last year.

Thai authorities estimate there are up to another 1.2 million unregistered migrants in the country who will not be eligible for the new process.

Human Rights Watch said the registration system left migrants open to abuse.

Unscrupulous officials and employers will now be able to threaten unregistered migrants with deportation in order to extort money, said the group’s Thailand expert Phil Robertson.

“The abuses against migrant workers will more than likely increase as a result of more migrant workers becoming undocumented and therefore vulnerable,” Robertson said.

The New York-based rights group released a report last week that documented a pattern of systemic abuse against migrant workers, from extrajudicial killings to torture, arbitrary arrest and extortion.

Burma citizens are particularly fearful, rights activists said, as a deal between Thailand and its military-ruled neighbour means they must return home to register, where the workers say they could face persecution.

Thailand’s government said a task force would be dispatched to deport unregistered workers but has not yet announced any firm plans to do so.<p></p>

“Immigration police and labour officials will check at every factory, and if they hire migrant workers without a permit then those people must be repatriated,” said another labour ministry official, Thanich Numnoi.

Thailand’s economy relies on migrant workers from its poorer neighbours, but in recent months the country has become tougher on immigration at its borders.

“This process doesn’t acknowledge the benefit or importance of these people for the economy,” said Andy Hall, a rights activist with the Bangkok-based Human Rights and Development Foundation.

“They need these people but they are not willing to give them their rights.”

Thailand, which is seeking a seat on the UN Human Rights Council, has been heavily criticised in recent months for its crackdowns on migrants from neighbouring Laos and Burma.

In December Bangkok sparked outrage when it defied global criticism and used troops to repatriate about 4,500 ethnic Hmong from camps on the border with communist Laos, including 158 recognised as refugees by the United Nations.

Earlier last year hundreds of ethnic Rohingya migrants from Burma were rescued in Indian and Indonesian waters after being pushed out to sea in rickety boats by the Thai military.