The currency attacked at the start of the 1997 Asian financial crisis was the Thai baht.
Thailand had maintained a de facto peg linking the baht closely to the U.S. dollar. Speculators questioned whether the country could defend that rate because Thailand had large foreign debts, a current-account deficit, and weakening financial institutions. After intense pressure, Thailand allowed the baht to float on July 2, 1997, and it rapidly lost value.
The crisis then spread through financial and currency markets in Indonesia, South Korea, Malaysia, and elsewhere. Investors withdrew capital, companies struggled to repay dollar-denominated loans, and several economies required international assistance. The International Monetary Fund organized major rescue programs, including one for Thailand.
The baht was the starting point, but the crisis was regional rather than confined to one country. A frequent mistake is to call it simply a stock-market crash: plunging equity prices were one part of a broader currency, banking, and debt crisis.