The conviction relates to an incident in 2016 in which a worker was seriously injured at Mannering.
The worker was driving a loader underground at the colliery when a damaged support strap hanging down from the roof struck his head near his left eye.
The incident left the employee with a severe head laceration that required medical treatment.
At the time of the incident, the mine was in a state of care and maintenance.
The court found the offence fell in the mid-range of objective seriousness and imposed a fine of $180,000 and ordered Lakecoal to pay the regulator's legal costs.
Related prosecution proceedings against LD Operations Pty Ltd are ongoing.
NSW Resources Regulator chief investigator Steve Orr said the judgement reflected community standards for mine safety.
"The court's decision sends a strong message that the community expects mine operators to comply with their work health and safety obligations," Orr said.
"This matter serves as a timely reminder to companies to ensure they have appropriate controls in place to protect workers."