Another Kentucky coal miner has died on the job. Twenty-six-year-old Ryan K. Thatcher of Salyersville was killed in a Martin County coal mine yesterday while operating a track locomotive pulling car loads of supplies into the mine.The mine is near Inez and is operated by Martin County Coal Company. It’s been closed while regulators investigate the accident.Thatcher’s death is the third coal mining-related fatality in Kentucky this year, and the tenth in the nation.