SEOUL, April 24 : Samsung Electronics' production of foundry and memory chips at its facilities in South Korea dropped 58 per cent and 18 per cent, respectively, during the overnight shift on Thursday as unionised workers attended a protest demanding higher wages, the company's union said. Many workers, who joined protest on Thursday at a factory complex in Pyeongtaek, south of Seoul, skipped the overnight shift from 10 p.m. Thursday to 6 a.m. Friday at the company's South Korean production