The appreciation of the local currency will hurt exports, and the foreign currency obtained by exports can only be exchanged for less local currency. In order to maintain the relative stability of the foreign economy, the country will choose to manage the exchange rate fluctuation to a certain extent, even if the floating exchange rate is restricted to some extent. When the market exchange rate seriously deviates from the normal exchange rate, the central bank will take measures to return the exchange rate to the normal range, in which using foreign exchange reserves is an effective method. When the demand of local currency for foreign currency rises, that is, when the local currency depreciates, the central bank will release a certain amount of foreign currency and exchange some local currency in the market, thus reducing the local currency in the market, that is. It can be said that a certain amount of foreign exchange reserves are reserved to maintain the credit of the local currency and prevent the local currency from depreciating. The economic collapse of both Japan and Thailand stems from currency devaluation.