Beware VinFast's meteoric rise – more than three-quarters of this year's SPAC debuts are trading below their float price

• VinFast soared more than 800% in one of the year's best market debuts until Tuesday.
• The value of the Vietnamese EV maker, which debuted via a SPAC merger, fell $83 billion that day.

VinFast's remarkable stock market debut derailed on Tuesday, wiping $83 billion off its value.

Its stunning rise since listing earlier this month was a rare bright spot for companies coming to market through SPACs, or special purpose acquisition companies.

More than three-quarters of firms that merged with a SPAC this year are now trading below the $10 level at which they go public, Bloomberg data showed.

That includes nine of the 11 companies that made their debuts in August – with the median loss standing at 41%, per the figures.

The billionaire founder of VinFast, Pham Nhat Vuong, has issued just 1% of its 2.32 billion shares to the public, leaving the Vietnamese EV maker subject to wild price swings.

"VinFast's current valuations are unsustainable," analyst David Blennerhassett told Bloomberg. "And because there are so few VinFast shares available, anyone who buys, say 50,000 shares, will move the stock."

Despite being unprofitable and only expecting to produce 50,000 cars this year, VinFast notched up a six-day winning streak prior to Tuesday's plunge with gains since its August 15 debut of more than 800%.

The stock fell another 11% on Wednesday but is up 6% premarket on Thursday.

Short-seller Jim Chanos isn't buying into the VinFast hype. He called it a "$200 billion meme stock" in a tweet on Monday.