* S.Korea shares set for eighth straight week of gains * Taiwanese dollar climbs to highest level since 1997 * Stock markets in Philippines, Indonesia closed for holiday By Pranav A K Dec 24 (Reuters) - South Korea led most emerging Asian stock markets higher in holiday-thinned trading on Thursday after the country signed deals to secure COVID-19 vaccines, while most regional currencies firmed against a softer dollar. Boosted by Seoul signing deals with Pfizer Inc and Johnson & Johnson"s Janssen to import vaccines, South Korea"s KOSPI hit a record high and was set to post an eighth straight week of gains, while the won jumped 0.4%. Asia"s fourth-largest economy, which had managed to contain the first two waves of virus, has buckled under the latest outbreak that emerged about two-weeks ago. Other big movers included India and Thailand"s exchanges, up 0.7% and 0.5%, respectively. In the United States, the S&P 500 eked out some gains despite worries over a pending stimulus deal and falling jobless claims, as investors rushed to economically vulnerable cyclical stocks on bets of a recovery from the global health crisis. "Wall Street clearly feels something positive will emerge from the veto/override/new vote mish mash on Capitol Hill at the moment. That sentiment has flowed through to Asian markets today," said Jeffrey Halley, senior market analyst for Asia Pacific at OANDA in Jakarta. "The Dow Jones had a strong-ish day and the Nasdaq fell, suggesting cyclical rotation which usually benefits Asian markets, given their weighting of cyclic stocks." China"s benchmark stock index slipped after the market regulator launched an antitrust investigation into tech giant Alibaba Group for suspected monopolistic behaviour. In currencies, the Taiwanese dollar outperformed peers again as it jumped to its highest level since 1997 and was on track for its best monthly gain since Feb 2017, consistently benefiting from strength in its tech exports this year. The Thai baht was largely unchanged, a day after the Bank of Thailand left the key interest rate unchanged and downgraded its 2021 growth forecasts. Trading volumes were thin across the region ahead of the Christmas holiday break, with stock markets in the Philippines and Indonesia shut on Thursday, while most regions will be closed on Friday except Thailand and China. HIGHLIGHTS ** Thailand"s 10-year government bond yields are up 1 basis point at 1.18% ** Top gainers on the Singapore STI include Wilmar International Ltd up 1.77%, Genting Singapore Ltd up 1.18% ** Top gainers on the Thailand"s SETI include Tata Steel Thailand PCL up 14.29%, Seamico Securities PCL up 13.33% Asia stock indexes and currencies at 0420 GMT COUNTRY FX RIC FX DAILY % FX YTD % INDEX STOCKS DAILY % STOCKS YTD % Japan -0.02 +4.87 0.41 12.59 China +0.15 +6.63 -0.21 10.66 India 0.00 -3.23 0.72 12.58 Malaysia +0.10 +0.79 -0.38 3.30 Philippines +0.00 +5.43 0.00 -7.82 S.Korea +0.43 +4.82 1.23 27.12 Singapore +0.06 +1.14 0.33 -11.79 Taiwan +1.54 +7.05 0.54 19.20 Thailand +0.07 -0.89 0.49 -9.9