HANOI, Aug 15 (Reuters) - Shares in Vietnamese electric vehicle maker VinFast (VFS.O) surged on their Nasdaq debut on Tuesday amid limited trading after the company closed its merger with a special purpose acquisition company (SPAC) in Asia's biggest M&A deal this year. The stock opened at $22, more than double the last close for VinFast's SPAC partner Black Spade Acquisition (BSAQ.A). The deal had valued VinFast at $23 billion. At one point on Tuesday morning, the stock traded as high as $24, which would have valued the EV start-up, which has not posted a profit, at $55 billion, more than Ford's (F.N) market capitalization at $48 billion. However, the volume of trading was negligible, with only 0.07% of shares changing hand in the first hour after the listing. VinFast's founder, Vietn