Undocumented workers had time until Saturday to register in Thailand. After June 30 those caught working illegally in Thailand will be fined between 5,000 Baht and 50,000 Baht, deported and banned from re-applying for a work permit in Thailand for two years.
Thai Royal Ordinance on foreign migrant workers 2560, employers found hiring illegal workers will be fined between 10,000-100,000 Baht per worker. If employers repeat the offense, they will be fined between 50,000-200,000 Baht or face no more than one year in jail, or both, and cannot employ workers for three years.
Read more about Thai Royal Ordinance