More than 1 million migrants living in Thailand face deportation unless they get official working papers by this Friday.

Around 2.5 million migrants live in Thailand, and while they are vital to Thailand's economy, many are in the country illegally and their time may be up.

The Thai government has set an arbitrary deadline for migrant workers from places like Burma, Cambodia and Laos.

Migration specialist Andy Hall says if they do not have legal documentation by December 14, they face deportation.

"[Thailand's government] basically said they will be rounded up and they will be deported back to their home countries and if they want to come in, they have to come in only through the legal channel," he said.

The Thai government introduced a system called "national verification" to allow illegal migrants to acquire legal status.

But the system can be cumbersome and expensive, and is already rife with corruption, as unscrupulous brokers and government staff extort money from illegal workers in return for the processing of paperwork.

"It's not really for the workers to apply themselves," Mr Hall said.

"It's more for the employers to apply on their behalf. So if employers don't apply, because they want the workers to stay unregulated so they can be exploited, the worker cannot apply.

"Also, the costs are very high. The process of this national verification is completely unregulated which means the costs are very high relative to the salary of the workers.

"And in addition, many of the workers, over 1 million, they're not eligible to apply for this process because they're not registered workers, they don't have any documents."

Policy experts say if the government cracks down on illegal migrants, then many will be exploited and forced underground.

Flow-on effect

Roisai Wongsuban, an advocacy expert who helps migrants, is very concerned about how children could be affected.

"If their parents get arrested, many children will be deported also and if the children have no right of staying in Thailand they will be the separation of family between children and migrant parents," she said.

"Migrants will be less empowered to negotiate in many factors of their lives. If they have children, they may feel very insecure to send children to school every day.

"So, it's just not only employment gap that will occur after December 14 but that also includes the feeling of safety and security of migration workers."

Migration experts say if the government proceeds with mass deportations, the Thai economy could be the biggest loser.

The economy in Thailand, a particularly labour-intensive export economy, is dependent on migrant workers from neighbouring countries, particularly Burma, that make up 70 to 80 per cent of the workers.

"And those economies are completely dependent also on unregulated irregular workers, people who don't have legal documents," Mr Hall said.

"It's not realistic for the government to deport these people because they are people who are making up a significant number of people in these industries."

Organisations working with migrants are still hoping the crackdown will be averted, and an amnesty will be offered before Friday.

They would like to see a 'bail-out' system, to allow unregistered migrants who present themselves at a Thai police station to stay until their application is processed.