Rating agency S&P upgraded Indonesia's sovereign credit outlook to 'BBB-' from 'BB+'. The move reflected its assessment of reduced risks to the country's fiscal position, the agency said.

"This is a well-deserved upgrade, thanks to its prioritization of fiscal sustainability at the expense of growth in 2016," said Trinh Nguyen, Senior Economist for Natixis, based in Hong Kong.

The upgrade would enable Indonesia to access a pool of eligible foreign investors that only invest in at least investment grade (IG)-rated asset, and provide a sentimental boost to equities and the economy, he added.

The Indonesian bond market received foreign inflows of $1.7 billion in April, data showed on Wednesday.

The index of Indonesia's 45 most liquid stocks gained as much as 4.2 percent to an all-time high.

The Indonesian benchmark ended 2.6 percent higher driven by financials and telecos. Telkom Indonesia jumped 5.1 percent after media reported that its unit Telkomsigma had entered the public cloud business under the Star Cloud brand.

Vietnam stocks ended at their highest in over nine years, logging a fourth week of gains, buoyed by financial and energy shares. Vietnam National Petroleum Group gained nearly 7 percent, driven by higher oil prices.

Rating agency Fitch on Thursday revised the outlook on Vietnam's long-term foreign- and local currency issuer default ratings (IDR) to 'positive' from 'stable'.

Meanwhile, other Southeast Asian markets largely ended in positive territory as concerns surrounding US politics waned and as traders shifted their focus to local catalysts.

Shares in Thailand and the Philippines ended marginally higher. However, the Philippine index posted a second week of losses.

Defying the broader trend, Singapore shares fell for a fourth straight session, recording their first weekly loss in three. Industrial stocks and telcos were the worst performers.