Malaysia was second with 11.8 million arrivals, up nearly 30% year-on-year, according to data from its tourism ministry.
Vietnam was third with 8.8 million visitors, up 58%, followed by Singapore with 8.24 million, a 31% increase.
Indonesia, which has the region’s largest economy, was fifth with 6.4 million, marking a 21% increase.
For the remaining countries, it ranged between 3.16 million for Cambodia and 600,000 for Myanmar.
According to industry insiders, Thailand regained its throne as the regional tourism champion after losing the title to Malaysia last year thanks to its visa waivers, including permanently for Chinese visitors.
Since July it has increased the number of countries and territories whose citizens can enter without visas and stay for two months from 57 to 93.
It also introduced the Destination Thailand Visa, which allows digital nomads, freelancers and visitors interested in learning skills such as cooking and martial arts to stay for up to 180 days.
Tourism competition is heating up in Southeast Asia with Laos, Indonesia and Malaysia announcing their own visa relaxation policies.