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Michael Lohan is a free man again ... 'cause TMZ has learned Lindsay's dad was released from jail early after serving time for violating his probation -- tied to his February arrest for allegedly beating up his ex, Kate Major .

A rep for the Palm Beach County Detention Center in Florida tells TMZ ... Michael was released around 1 AM on Sunday, October 5. We're told he scored early release -- 24 days off -- thanks to "gain time" earned from working inside the jail as a trustee inmate. Palm Beach County Sheriff's Office

Lohan checked in around April and was expected to serve roughly nine months. His probation violation stemmed from the Texas arrest, where he was hit with a felony continuous violence against the family charge. That case, we're told, is still pending.

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