Which index lost about 80% of its value during Thailand’s 1997 Asian financial crisis?

The Stock Exchange of Thailand Index lost about 80% of its value during Thailand’s 1997 Asian financial crisis.

Thailand’s stock market had risen during years of rapid growth, property speculation and large foreign capital inflows. When confidence weakened, investors withdrew funds and the country struggled to defend its currency peg. The baht was floated in July 1997, and the financial shock spread through banks, finance companies and equity markets.

The Thai stock index fell dramatically from its 1990s peak to its crisis-era low. The collapse was part of a wider regional contagion affecting Indonesia, South Korea, Malaysia, the Philippines and other economies. The International Monetary Fund arranged a rescue program for Thailand, conditional on financial and economic reforms.

The exact percentage depends on the start and end dates used, so “about 80%” is the standard rounded description. This question concerns Thailand’s own benchmark, not the Hang Seng Index in Hong Kong or Japan’s Nikkei 225. The crisis also involved currencies and banking systems, not only share prices.