A total of 446,936 foreign tourists visited Thailand from May 1 to 8, down 22.23% year on year, the Tourism and Sports Ministry said on Tuesday.
It blamed the drop on the end of long holidays in many regions, signalling the start of the low season.
Thailand welcomed 9.04 million foreign visitors from January 1 to May 8 this year, generating 373.30 billion baht in tourism revenue, it added.
The ministry expects 2 million foreign tourists to visit Thailand in May, mostly from countries in Asean, East Asia and South Asia.
The top five tourism markets for Thailand in May so far are Malaysia (73,215 visitors), China (64,887), India (30,784), Laos (22,619) and South Korea (22,107).
"Visitors from Malaysia, China, India, Laos and South Korea accounted for 47.8% of all foreign arrivals," the ministry said.
It added that visitors from Laos increased by 32.45% year on year, but arrivals from Malaysia, China, India and South Korea dropped by 37.52%, 34.39%, 15.22% and 8.32% respectively.
The ministry said it expects foreign arrivals – especially from China and Australia – to rise in the latter part of May on signs of a tourism recovery.
Airports of Thailand is currently in talks with airlines on increasing their landing slots.
Thai agencies are also promoting awareness of the visa process among Chinese tour agencies and visitors, the ministry added.