The Indonesian rupiah hit a near five-week high on Wednesday as risk appetite returned to financial markets, while other Asian emerging currencies were largely mixed as the Omicron COVID-19 variant continued to cloud the outlook for economic recovery.

The South Korean won firmed by up to 0.3% after softening for two straight days, and the Malaysian ringgit and Singapore dollar posted small gains, while the Philippine peso and Thai baht each fell 0.2%.

Indonesia's rupiah, one of the most risk-sensitive currencies in the region, strengthened more than 0.5% to touch 14,230 per dollar, its highest level since mid-November. Ten-year benchmark yields were largely flat, but hovered around their two-week high levels.

"In Asia, most currencies including rupiah, ringgit, Singapore dollar, China's yuan and Indian rupee benefited from a return in risk appetite," analysts at Mizuho Bank said.

Analysts at Australia and New Zealand Banking Group expect the rupiah to weather the US Federal Reserve's policy normalisation, assuming no material impact from the Omicron variant. They expect the currency to reach 14,000 per dollar by end-2022.

Elsewhere, the Thai baht remained under pressure ahead of a central bank policy decision later in the day. The Bank of Thailand (BoT) is expected to hold interest rates at a record low to bolster the tourism-dependent economy, according to a Reuters poll.

The BoT is under no pressure to remove its accommodative policy stance considering the fragile recovery which has taken hold so far in 2021, and may remain as tentative into 2022, Mizuho Bank analysts said in a note.

Meanwhile, Thailand approved a new package of economic stimulus measures, including tax breaks for shoppers, in a bid to revive its economy, grappling with the pandemic-induced collapse of its vital tourism sector.

Asian markets elsewhere gained ground as investors picked up riskier assets, with the MSCI's broadest index of Asia-Pacific shares outside Japan gaining 0.6% after an upbeat overnight Wall Street session.

The US dollar index, which measures the currency against major peers, was last at 96.516, down from as high as 96.994 last week, as investors favoured riskier currencies and asset classes.

All regional equities logged modest gains, with top gainer Thai shares up 0.6% ahead of the central bank decision, while Malaysia, the Philippines Singapore and Indonesia added about 0.5% each.