SEOUL (Reuters) - Hyundai Motor Co has reached a tentative wage deal with its South Korean labor union, a union spokesman said on Thursday. Should the union's members approve the deal in a vote on Monday, Hyundai, which along with affiliate Kia Motors ranks as the world's fifth-biggest carmaker, should avoid further production losses. Hyundai had suffered a series of stoppages since August 20 that prevented it making 50,191 vehicles worth 1.02 trillion Korean won, though it has usually recouped lost production with overtime and weekend work. The latest deal included bonuses and other payments totaling 8.5 million Korean won ($7,800), equivalent to five times the monthly base wage, and a 5.14 percent rise in basic salaries, a union spokesman said. The company rejected the union's demand for a 56.25 gram gold medal - worth about $2,400 at today's prices - and a bonus of two months' salary for those with at least 40 years of continuous service, as well as 10 million won for each worker whose children opt not to attend college, the spokesman said. Instead, those who retire after more than 40 years of service will receive 6 million won, he said. "Hyundai's labor union showed a mature attitude during talks, retracting unreasonable demands given public criticism and concerns," the company said in a statement. Hyundai's domestic sales slumped 20 percent in August from the previous month and its exports slipped 9 percent, although year-on-year sales went up because of longer walkouts a year earlier. The union representing Hyundai's South Korean workers has staged strikes almost every year in its 26-year history, except for a three-year hiatus from 2009 to 2011. Moon Yong-moon, the hardline union chief who last year led the strike at Hyundai for the first time in four years, will see his term expire this month. He said in a statement last week he would not run for reelection. ($1 = 1094.5500 Korean won) (Reporting by Hyunjoo Jin; Editing by David Holmes)