The Foreign Office has warned travellers to exercise extreme caution after 65,000 protestors hit the streets of Bangkok over the weekend.
The anti-government campaigners are supporters of ousted former premier Thaksin Shinawatra, the one-time owner of Manchester City.
Shinawatra, a self-exiled former telecommunications tycoon, was ousted in a coup and convicted of corruption in his absence.
The red-shirt protesters say the current government is illegitimate and want current Prime Minister Abhisit Vejajjiva to step down.
The protestors completed a 28-mile route through the city, handing out leaflets to bystanders, but kept the protest peaceful.
The Foreign Office advised British travellers to take extra care when travelling around the city and stay indoors if violence breaks out.
Luxury tour operator Kuoni said travellers had only suffered “minimal disruption”.
Director of product for Asia Wendy Kenneally said: “To date, the protests have been largely peaceful and tourists have not been affected.
“Kuoni kept customers informed and those in Bangkok continued their holiday with minimal disruption and customers in other parts of the country have been able to continue their holiday totally unaffected. Looking forward, booking patterns continue as normal.”
Protest leaders said they would remain in the capital for at least two weeks.