SEOUL, Oct 15 (Reuters) - Shares of Big Hit Entertainment , the management label of hugely popular South Korean boy band BTS, debuted at double its IPO price on Thursday, as investors chased South Korea’s largest listing in three years. Big Hit shares opened at 270,000 won, compared to an initial public offering (IPO) price of 135,000 won per share last month, at the top of its indicative range.