Southeast Asia's Grab slumps in U.S. debut after record SPAC deal Summary Grab listed on Thursday after $40 bln deal with Altimeter Debut marks biggest U.S. listing by a Southeast Asian firm Early backers SoftBank, Didi set for payday bonanza Bell-ringing ceremony takes place in Singapore SINGAPORE, Dec 2 (Reuters) - Shares in Grab , Southeast Asia's biggest ride-hailing and delivery firm, slid more than 20% in their Nasdaq debut on Thursday following the company's record $40 billion merger with a blank-check company. Grab's shares rose as much as 21% minutes after the listing before retreating to trade 23% lower at $8.51 by 1834 GMT. "The price makes no difference to me. I'm going to celebrate tonight and get back to work tomorrow," Chief Executive Anthony Tan told Reuters just after the