Tired returnees stepped off Thai police trucks and buses in the border town of Poipet in northwestern Banteay Meanchey province where they received a free meal before embarking on the final leg of their journey.
The mass exodus of labourers -- who play a key role in prominent Thai industries but often lack official work permits -- was sparked by an army warning that illegal foreign workers would be arrested and deported.
The International Organization for Migration (IOM) confirmed the figure.
Around 10,000 workers arrived in Poipet today alone where they were given rice, pork and water as they waited for Cambodian military trucks to ferry them home, Sarouet said.
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The main route out of the border town was packed with vehicles driving the labourers and their families to provinces across the country in an operation which will continue until midnight.
Seng Phoan, a 28-year-old construction worker who spent around two months in Thailand, was returning to the northwestern province of Battambang as part of the Cambodian army convoy.
"I was worried about my safety. If I can find work here I will not go back to Thailand," Seng added.
Thailand is usually home to around three million migrant workers, according to the IOM, with an estimated 180,000 unofficial Cambodian labourers. Many work in seafood and agriculture industries.
The junta has dismissed as "rumours" it was forcing Cambodian labourers out of the country after issuing a warning last week that it viewed illegal migrants as a "threat" who faced arrest and deportation.