Seoul came second, followed by Taipei and Hong Kong, according to the Dutch-based agency that compiled the list based on check-in dates between Sept. 1 and 4.
The rest of the list was made up of Tokyo, Kuala Lumpur, Sydney, Ubud, and Chiang Mai.
This year, the government chose to begin the holiday one day before the official day on Sept. 2 so that it would be spaced apart from the first day of the new school year on Sept. 5.
As the holiday will fall on the weekend, it will be a four-day holiday in total.
Thailand recorded 15.32 million foreign arrivals between January and July this year, Reuters reported.
The country currently offers visa exemptions for over 50 countries, including Vietnam, for stays of up to 30 days.
A trip to Thailand now costs VND5-7 million ($200-$300), making it affordable for many Vietnamese travelers.