Thailand's top five markets were Malaysia (4.5 million), China (4.4 million), India (2.4 million), Russia (1.8 million) and South Korea (1.5 million), Bangkok Post reported.
International tourism revenue dropped 4.71% to 1.53 trillion baht (US$48.8 billion).
Malaysia welcomed 38.3 million foreign arrivals in the first 11 months of 2025, exceeding the total recorded for the whole of 2024, according to Tourism Malaysia under the Ministry of Tourism, Arts and Culture.
Once a tourism powerhouse in Southeast Asia, Thailand struggled with a series of challenges last year.
The crisis began in January as many Chinese tourists canceled their trips to the country following the high-profile abduction of Chinese actor Xing Xing.
Two months later a deadly earthquake in Myanmar that sent tremors across Bangkok caused widespread damage to the tourism industry.
Escalating military clashes along the Thai-Cambodian border also triggered a surge in cancellations across provinces near the fighting. Some countries warned their citizens to postpone traveling to Thailand.
Vietnam ranked third in the region in terms of arrivals after receiving a record 21.2 million tourists last year.