Nearly 200 Cambodian migrant workers who were scammed by their broker and then abandoned south of Bangkok earlier this week are among the latest victims falling between the cracks of an ill-defined labour registration system, according to rights experts.

The 180 Cambodian migrants were taken to southern Thailand on Tuesday by a broker promising factory jobs for 300 baht ($9) a day, Thai media reported.

Told they were en route to register for employment documents, the workers were instead dumped in a field around 2am on Wednesday morning, said Sim Sam Arth, chief of the Poipet immigration office.

Some of those defrauded held passports, and thought they were migrating legally to Thailand. But the neighbouring countries are still at odds about the legal system, and while they signed a memorandum of understanding in June, the announced process is still not in place, monitors said. Instead, workers are entering a risky grey area reliant on their employer registering them for temporary work and residency cards.

“The present situation leaves hundreds of thousands of Cambodian migrants in a limbo where it is not clear if they can be deported back at any time,” said Sara Piazzano, country director of the USAID-funded Counter-Trafficking in Persons Project. “It is really urgent that the Thai and Cambodian Governments find an agreement on these procedures.”

But according to the Ministry of Foreign Affairs, the current registration system is seeing Cambodian workers pour back into Thailand. More than 420,000 have been granted legal working status, while another 270,000 have temporary status, Foreign Ministry spokesman Koy Kuong said yesterday after a meeting with the Thai ambassador.

The figures represent a huge leap beyond any previous tallies; in June, the government estimated 450,000 undocumented Cambodians had worked in Thailand before the post-coup exodus, only 90,000 of whom were documented.