Concerns about slowing global growth returned to the fore with data from Philippines and Thailand underscoring the challenge facing Asia's export engines.
The peso lost ground after the country reported a wider trade deficit while the baht came under pressure from a weaker-than-expected July factory output reading.
The Malaysian ringgit shed on interbank speculators' selling, while the South Korean won eased as importers sought dollars despite the approaching month-end. Offshore funds sold the Singapore dollar.
Other riskier assets such as Asian shares and the Australian dollar retreated as investors waited for a gathering of central bankers and economists at Jackson Hole, Wyoming, keeping an eye on clues on stimulus measures from the Federal Reserve Chairman Ben Bernanke's speech on Friday.
"More investors appeared to scale back expectations that the Fed would s how anything this week," said Jeong My-young, Samsung Futures' research head in Seoul.
"Before making any steps or a clear signal, the Fed will want to see August job data due early next month, especially given recent strong economic indicators. It may be also awkward for the Fed to do something before the ECB takes any steps," Jeong added.
The US August non-farm payrolls is set to be released on Sept. 7, while the ECB is expected to reveal more details to lower the debt yields of Spain and Italy after its Sept. 6 policy meeting although its implementation is likely to start in late September at the earliest.
Since late July, most emerging Asian currencies have been supported from expectations that the Fed and the European Central Bank would take measures to shore up the global economy and to ease the euro zone's debt crisis.
Amid deceleration in the United States and China, on top of the European fiscal problems, Japan's government cut its assessment for the export-driven economy, for the first time since October 2011.
RINGGIT
The ringgit shed as interbank speculators sold it amid weaker euro and Australian dollar.
Technically, the Malaysian currency had been seen having room to weaken to 3.1276 per dollar, a 100-day moving average.
But domestic exporters and oil companies bought the local unit around 3.1250, helping the local unit recover some losses, dealers said.
PHILIPPINE PESO
The Philippine peso fell with increasing trade deficit and on dollar demand linked to non-deliverable forwards (NDFs) fixing, dealers said.
Philippines' June imports growth hit a 10-month high with a trade deficit of $787 million raising the six-month trade shortfall to $4.0 billion, data showed earlier.
The peso also came under pressure from catch-up selling after the country's financial markets were closed for a holiday on Monday.
"At the moment, the dollar will remain biddish due to weakening economic data coming out of Asia," said a European bank dealer in Manila, adding the peso is seen weakening to 42.40 per dollar.
"There is a very high chance of disappointment from the Jackson Hole meeting as many analysts are also saying that the situation in the US is not yet that dire to warrant another round of QE," the dealer added, referring to the Fed's bond-buying programme or quantitative easing.
BAHT
The baht retreated, tracking weakness in its Asian peers and after data showed Thai manufacturing production in July fell more than expected.
The country's factory output fell 5.82 percent in July from a year earlier, worse than a 3.5 percent decline forecast of a Reuters poll.
WON
The won slipped as South Korean importers bought dollars for payments and traders added dollar holdings.
Still, the South Korean currency found some relief from exporters' demand for month-end settlements.
It also has technical support at 1,138.8 per dollar where the 50.0 percent Fibonacci retracement of its appreciation between late July and early August, as well as the kijun line on the daily Ichimoku chart sit.
SINGAPORE DOLLAR
The Singapore dollar eased on selling from real money funds and model accounts, trying to clear a technical support line at 1.2554 to US dollar, the 61.8 percent retracement of the appreciation between late July and early August.
The city-state's currency is seen heading to 1.2590, the 76.4 percent level once the retracement is decisively broken.
But the Singapore dollar recovered some of initial losses as some investors took profits from the greenback.