Authorities in Thailand are involved in a massive crackdown on migrant workers, who they said were stealing jobs reserved for Thai nationals. It is feared that the anti-immigration sentiment is growing in the country as its economy remains stagnant.

Thailand launched an operation – led by its Labour and Immigration Departments – and raided local markets to nab potential migrant workers who have breached local labour laws.

Approximately 14 people were arrested following a raid at a vegetable market in Bangkok on Wednesday (28 September). The migrants were believed to be from Vietnam and Cambodia, but a majority of them were from Myanmar.

"We have received many complaints about illegal immigrants working in markets including Vietnamese and even South Asians who were stealing jobs from Thais," Thai immigration police chief Nathorn Phrosunthorn said. "They should be doing the jobs that Thais don't want to do like – work as house cleaners."

Around 153 migrant workers have been arrested since the raids began in early September as police and labour officials continue to target local markets, restaurants, supermarkets and shopping malls. Some of those caught were slapped with a five-year jail term and a fine of up to TBH3,000 ($100) or face deportation.

According to a memorandum of understanding signed in 2015, Vietnam nationals in Thailand were permitted to take up jobs only as manual labourers in the fishing or construction industries. It is estimated that Thailand has more than three million migrant workers.

As the Southeast Asian country's economy grew in the late 1990s, thousands of migrants from surrounding countries moved to Thailand to take up jobs that Thais were little interested in – like working in the fishing industry or in construction.

But as the country's economy started to shrink, fears of migrant workers causing unemployment for Thai nationals have reportedly set in.

"There seems to be a surge of national sentiment in Thai immigration policy claiming migrants from Vietnam, for example, are taking jobs that are reserved for Thai nationals," Sunai Phasuk from Human Rights Watch told Reuters. "We haven't seen this kind of rise in anti-immigrant sentiment for decades. This has a lot to do economic concerns."

However, defending the crackdown, Nathorn said it was aimed at driving out migrant labourers. "We still need migrant labour. We just want to keep some order," he said.

Sanit Choklamlert, a local shop keeper in Bangkok feels that some migrants come across as heavy competitors for locals.

"There are too many Myanmar people here now and they're fighting for the same job as us. We need to send some back," he said.