Which 1997 crisis began in Thailand after the baht was allowed to float and spread across East Asian markets?

The 1997 crisis that began in Thailand after the baht was allowed to float was the Asian financial crisis.

Thailand abandoned its fixed exchange-rate policy on July 2, 1997, after intense pressure on the baht. The currency depreciated sharply, and investor confidence weakened across several economies whose banks and companies had borrowed heavily in foreign currencies. Stock markets and exchange rates then came under severe pressure in Indonesia, South Korea, Malaysia, and elsewhere.

The crisis was not simply a stock-market event. Currency devaluations, banking failures, corporate debt, capital flight, and recession reinforced one another. The International Monetary Fund arranged assistance programmes for several affected countries, including Thailand, Indonesia, and South Korea.

It is sometimes called the Asian currency crisis because exchange rates were central to the turmoil. “Asian financial crisis” is broader and more precise: the shock affected financial systems, companies, employment, and government policy as well as share prices.