2020 and 2021 are not favorable years for the aviation industry due to the Covid-19 pandemic, so this ranking is taken from a 23-month survey (from September 2019 to July 2021) to give the best results.
Here are the 5 airlines with the highest ratings:

  • 1st – Singapore Airlines (1st in Asia and 2nd Worldwide)

Singapore Airlines is the flag carrier airline of Singapore with its hub at Singapore Changi Airport. It has been ranked as the world’s best airline by Skytrax four times and topped Travel & Leisure’s best airline rankings for more than 20 years.

  • 2nd – Garuda Indonesia (8th in Asia and 15th Worldwide)

Garuda Indonesia is the flag carrier of Indonesia, headquartered at Soekarno–Hatta International Airport. A successor of KLM Interinsulair Bedrijf, it is a member of SkyTeam and the second-largest airline of Indonesia after Lion Air, operating scheduled flights to a number of destinations across Asia, Europe, and Australia from its hubs, focus cities, as well as other cities for Hajj. It is the only Indonesian airline that flies to European airspace.

  • 3rd – Bangkok Airways (9th in Asia and 19th Worldwide)

Bangkok Airways Public Company Limited is a regional airline based in Bangkok, Thailand. It operates scheduled services to destinations in Thailand, Cambodia, China, Hong Kong, India, Laos, Malaysia, Maldives, Myanmar, Singapore, and Vietnam.

  • 4th – Thai Airways (23rd Worldwide)

Thai Airways International is the national airline of Thailand, with main base at Bangkok’s Suvarnabhumi International Airport, and a founding member of the Star Alliance.

  • 5th – AirAsia (29th Worldwide)

AirAsia is a low-cost airline based in Kuala Lumpur, Malaysia. It specializes in scheduled domestic and international flights. It is Asia’s leading low-fare airline. Also, it is the first airline in the Asia-Pacific region to use e-tickets.

According to Wikipedia and flyingdogtravel.com

(https://flyingdogtravel.com/2021/09/29/best-southeast-asia-airlines-2021/)