* Buys Iran's Kangan condensate for first time since H1 2012 * Replacing Iran's oil slashed profits * Cargo to arrive at South Korean plant in March (Adds Total reaction) By Florence Tan and Seng Li Peng and Meeyoung Cho SINGAPORE/SEOUL, Jan 25 (Reuters) - South Korea's Samsung Total Petrochemicals (STC) has revived a contract to buy Iranian oil after a year's hiatus, as thin margins in plastics make the cheap fuel from Iran hard to resist, people familiar with the deal said on Friday.