Sudarat Thongsopa was apprehended at an unregistered house in Na Tan district on Saturday in an extended investigation into the arrest of Chamras Chuikrajai on a charge of human trafficking in October last year.
The Criminal Court issued a warrant for Ms Sudarat's arrest on Nov 28.
According to a police investigation, she was part of a gang involved in the trafficking of a group of migrant workers whose pickup truck lost control and hit a tree on a slippery road in Buri Ram province in October last year.
A total of 21 migrant workers were killed in the crash.
Ms Sudarat denied she was part of the ring, saying all the workers, mostly from Laos, had proper travel documents.
She said she was paid for providing shelter and food for the immigrants. They would later be picked up and sent to other provinces including Prachuap Khiri Khan, Samut Sakhon and Samut Prakan to work.
She was charged with providing shelter to illegal immigrants.