Singapore ranked sixth with a satisfaction rating of 90% while Vietnam was 10th with 87%.
The survey asked 170,000 travelers to rate their favorite destinations around the world.
Portugal was the highest rated at 94%, followed by the Cook Islands, a country in the South Pacific, and Australia.
The others in the list were Japan, Spain, Greece, Ireland, and Turkey.
"A gem of Southeast Asia, Vietnam is a safe, affordable and experience-rich country suitable for travelers of all ages and abilities," Flight Centre wrote.
Singapore is famous for its strict laws and low crime rates.
Vietnam has received 11.4 million foreign visitors so far this year, 1% more than in pre-Covid years, with South Koreans and Chinese driving the increase.
For the full year it targets 18 million.