The Southeast Asian destination welcomed 514,244 British travellers between January 1 and June 10, representing a modest decline of 3.16 per cent compared to the same period last year.
However, tourism chiefs insist the figures reflect flight capacity challenges rather than weakening demand from UK holidaymakers.
Speaking at the Thailand Travel Mart Plus (TTM+) trade show in Pattaya, Tourism Authority of Thailand (TAT) deputy governor Chiravadee Khunsub said the British market remained one of the country's strongest and most loyal.
She said: "These numbers show how robust the UK market is, as it shows there is not a lack of demand but more a lack of supply as Middle Eastern airlines make up 30% of our airlift."
The slight slowdown comes after a record-breaking 2025, when UK arrivals to Thailand surpassed one million visitors for the first time since the pandemic.
TAT used this year's trade gathering to launch its new "Healing is the new luxury" campaign, designed to promote responsible tourism and encourage visitors to embrace slower, more authentic experiences.
The initiative aims to move Thailand's tourism industry away from a focus on visitor numbers alone, instead encouraging travellers to stay longer and explore the country's lesser-known destinations.
With British repeat business accounting for almost 70 per cent of arrivals, tourism officials believe now is the perfect opportunity to showcase a different side of Thailand.
Khunsub said: "Repeat business is at nearly 70%, so we know UK travellers are incredibly loyal. Therefore, we are trying hard to promote secondary hubs, such as swapping Chiang Mai for Chiang Rai or Phuket for Krabi."
Thailand has also benefited from the growing trend for "set-jetting", with travellers inspired by film and television locations.
The latest series of 'The White Lotus' has sparked increased interest in Koh Samui, while Krabi has enjoyed renewed attention following its appearance in 'Jurassic World Rebirth'.
Improved air connectivity is also expected to boost British arrivals later this year.
Virgin Atlantic is set to launch a seasonal three-times-weekly service between London Heathrow and Phuket from October 18 through to April 2027.
Meanwhile, Norse Atlantic Airways will introduce five weekly flights from London Gatwick to Bangkok over the same winter period, while TUI has increased its winter programme to Phuket from two to three weekly departures from Gatwick.
The tourism authority is also strengthening its support for the trade sector, adding an AI-powered assistant to its Thailand Expert training platform and planning a series of virtual webinars for agents.
Held in Pattaya between June 10 and 12, this year's TTM+ attracted more than 950 delegates, including 429 buyers and 428 sellers from established markets such as Europe, North America and Australia, alongside emerging regions including South America, the Middle East and eastern Europe.
Despite short-term challenges linked to reduced flight capacity, Thailand remains confident that British travellers are eager to return, particularly as the destination broadens its appeal beyond its famous beaches and bustling cities.
