The hostage taking drama continued until Thursday while police tried to negotiate for the workers to end the protest.
At the height of the protest, the number of protesters grew to about 1,000 and they also took the manager of the plant and a police officer, Pol Sgt Thongsuk Thongthai, hostages.
The factory is located in Tambon Kanju in Bueng Samphan district.
The protesters released the manager late at night and released the policeman in the morning but they continued to hold the security officer hostage.
The protesters claimed that their peers were harmed by security officers of the plant and they demanded better living and working conditions.
At press time, the number protesters dropped to about 400 and the tension has eased, police said.