SEOUL (Reuters) - Hyundai Motor Co's <005380.KS> unionized workers in South Korea voted in favor of a wage deal by a slim margin, averting more strikes in the automaker's biggest manufacturing base. A total of 51.5 percent of Hyundai Motor voters approved the preliminary agreement reached on Monday, while 48.1 percent rejected the deal, a union spokesman said on Thursday. The 47,000-member union resumed a partial strike last week after Hyundai Motor, Kia Motors and Hyundai Mobis <012330.KS> bid $10 billion for a plot of land in Seoul, more than three times its appraised value. Hyundai, the world's fifth-biggest automaker alongside with Kia Motors <000270.KS>, has been hit by strikes in all but four years of its South Korean union's 27-year history. The latest wage agreement includes bonuses and incentives totaling 8.9 million won, plus payments equivalent to four and a half months' salary - a smaller rise than last year's, the company has said. The two sides failed to agree on when the automaker will start revamping its wage calculation scheme, a key demand by the union which was at the bone of contention during this year's wage talks. The vote results on Thursday makes its affiliate Kia Motors <000270.KS> the only automaker in South Korea which has yet to reach an annual wage agreement with its labor union. Kia's unionized workers in South Korea continued a partial strike this week, demanding that the automaker count regular bonuses as base wages. (Reporting by Hyunjoo Jin; Editing by Bernard Orr)