The Indonesian rupiah fell against the dollar on local banks' dollar demand, while the South Korean won slid on selling from offshore funds.
Macro accounts sold the Singapore dollar amid talk of intervention. The Malaysian ringgit weakened on dollar bids for daily fixing.
Emerging Asian currencies slid versus the yen although the Bank of Japan delivered its third dose of monetary stimulus in four months earlier in the day, a suspected prelude to more aggressive action next year.
"Investors adjusted positions to book profits after the BOJ's easing before the year-end and they got what they have wanted to some degree," said Jeong My-young, Samsung Futures research head in Seoul.
"But they will keep squeezing the BOJ," said Jeong, adding that expectations for BOJ easing will continue to support emerging Asian currencies.
Regional units have risen against the yen as the Bank of Japan is expected to take bold monetary policy measures in the face of intensifying pressure from the incoming prime minister to beat deflation.
On Wednesday, the Singapore dollar hit 1.4397 to 100 yen, its strongest since October 2008.
RUPIAH
The rupiah fell as Indonesian local banks bought dollars on behalf of local corporates.
Rupiah market prices against to the dollar were weaker than indicative prices, but the central bank was spotted preventing further depreciation, dealers said.
The rupiah slid 0.2 percent to 9,665 to the dollar on tradings screens, but dollar bids were placed at around 9,740-9,750, according to Jakarta-based dealers. Bank Indonesia sold dollars below 9,700, they added.
Some banks in Indonesia bought currencies such as euro and yen, converting them later to meet their dollar needs, dealers said, adding that the banks attempted to keep their trades discreet so the central bank would not prevent them to stem rupiah weakness.
WON
The won eased on dollar demand from offshore funds and importers, with currency investors showing muted reactions to the election of Park Geun-hye as president.
SINGAPORE DOLLAR
The Singapore dollar slid on selling from macro accounts and the central bank was spotted buying US dollar through agent banks around 1.2190, dealers said.
The city-state's currency also came under pressure from option-linked selling between 1.2180 and 1.2185 to the dollar, but it found some relief on corporate demand around 1.2220.
RINGGIT
The ringgit eased on fixing-related dollar demand, dealers said, while local pension funds looked to buy the greenback at below 3.0600 to the Malaysian currency.
Center>Copyright Reuters, 2012