South Korea has given permission to 300,000 illegal migrant workers including 120,000 Thais to leave the country without being blacklisted.
The so-called voluntary departure programme started on Monday and will last until March 31.
Those who agree to leave South Korea during this time will be pardoned for their "wrongdoing", Seoul officials said.
Furthermore, they will not be blacklisted by South Korea's immigration authorities, according to an announcement published on the website of the Korea Immigration Service.
The announcement came in six languages -- Korean, English, Thai, Russian, Chinese and Vietnamese.
After the given pardon period, those who remain in South Korea illegally, if arrested, will be immediately deported, blacklisted and prohibited from re-entering for 10 years, the announcement read.
The number of Thais travelling to South Korea as tourists who ended up overstaying as illegal labourers has increased by hundreds of thousands in recent years.
Only about 25,000 workers are currently hired to work legally in South Korea, according to Busadee Santipitaks, spokeswoman for the Ministry of Foreign Affairs.
The decision came last Friday, when Labour Minister Adul Sangsingkeo led a delegation of labour officials to South Korea for talks.
One of the topics on the table was the issue of illegal Thai migrant workers.
Thai delegates met South Korean Justice Minister Park Sang-gi and Korea Immigration Service commissioner Cha Gyu-geun to negotiate the return of the illegal workers.
The Thai delegation also submitted a request to South Korean officials to expand South Korea's quota for Thai workers to work in the country.
The quota is capped at 5,000 a year.
Other requests made at the meeting were to raise the maximum age limit from 39 and allow another round of work permit renewals.
Thai workers are now allowed to have their permits renewed up to two times, for four years and 10 months per renewal.
The officials reportedly agreed to consider the submitted requests.
The Thai delegation met Human Resources Development Service of Korea (HRD Korea) President Dong Man Kim and Kim Dong-ho, deputy director of the Foreign Workforce Division.
The Labour Ministry will hold a meeting today with the Ministry of Foreign Affairs, the Thai embassy in South Korea and other concerned agencies to discuss measures to encourage illegal Thai migrant workers to enter the voluntary departure programme being offered.
The ministry said those who leave on the departure programme can go back to work in South Korea through the government-to-government Employment Permit System.
Despite these promises, some illegal Thai migrants fear the South Korean government will not grant them re-entry if they leave, according to reports.