But experts say governments are managing the losses better than they did in the past.
The currencies of China, India, Indonesia and Myanmar all have lost value since January of 2018. The Indian rupee was at a record low against the U.S. dollar in June. And the Chinese yuan lost 3.2 percent in the first half of the year.
Economists say there are many reasons for this, including possible contagion from financial problems in Turkey. They also say investors are worried about the effects of the trade dispute between the United States and China.
Next week, China will face additional U.S. tariffs on $16 billion-worth of Chinese products.
Song Seng Wun is an economist with investment bank CIMB in Singapore. He said, "It's just basically that everything we've worried about now and then sort of converged."
宋诚焕（Song Seng Wun）是新加坡联昌国际银行（CIMB）的经济学家。他表示，“基本上我们时常担心的问题都凑到一起了。”
Why are Asian currencies losing value?
Experts say there is no single reason currency exchange values are lower in Asia. Rising oil prices may have affected the Indian rupee for example. Myanmar has had large growth in imported products.
In Vietnam, Bao Viet Securities, a financial business, said Vietnam's currency has lost value because the value of the currencies of neighboring countries have gone down.
在越南，保越证券(Bao Viet Securities)表示，越南货币贬值是因为邻国货币贬值。
But it is the fall of Turkey's lira and the possibility that it could bring down other currencies that has caused problems in Asian currency markets, Song said.
The continuing trade dispute between the U.S. and China is another reason for the currency problems.
Some media reports have said that the U.S.-China trade war has caused investors in India to move away from local stocks and similar assets.
Maxfield Brown is an expert with the business services company Dezan Shira & Associates. He spoke about the exchange value of Vietnam's currency.
麦克斯菲尔德·布朗（Maxfield Brown）是协理管理咨询公司(Dezan Shira & Associates)的一名专家。他谈到了越南货币的汇率。
"I think there's a number of reasons why it could be going down," he said.
Brown said Vietnamese officials are frightened about recent U.S. and Chinese actions and everyone is being cautious.
Learning from mistakes in the past
Financial officials of some Asian governments have answered market uncertainty by raising interest rates. Raising rates usually increases the exchange value of a currency.
Indonesia has raised important interest rates four times in three months. India and the Philippines have also raised rates.
Asian countries are keeping more foreign currency in their banks and trying to lessen national debts, said Marie Diron. She is a director of Moody's Investor Services in Singapore.
穆迪投资者服务公司(Moody 's Investors Service)驻新加坡负责人玛丽·迪隆(Marie Diron)表示，亚洲国家正在加大外汇储备并试图降低国债。
She said actions like raising rates help to control falls in currency values.
In Vietnam, government officials learned from bad currency decisions in the past and now their answers are "measured," Brown said.
The French investment bank Narixis said Friday that China will likely take measures to support the economy. These actions should also help calm international financial markets.
Most economists agree this is not a time of crisis. Asian currency falls are not a threat to the world's economy, Song said.
I'm Susan Shand.