The British Foreign & Commonwealth Office (FCO) has updated information for travellers heading to Thailand.
However, officials at the body have stopped short of issuing a travel warning for the destination.
The move follows the fatal shooting of London City trader Stephen Ashton on Koh Phangan on January 1st.
“Western tourists have been victims of vicious, unprovoked attacks by gangs in Koh Phangan,” explained Foreign Office information.
“These attacks are particularly common around the time of the Full Moon parties and generally occur late at night near bars in Haad Rin on Koh Phangan.
“Exercise caution when in this area at any time, especially after dark.”
Seven British nationals have been murdered in Thailand since January 2009.
In the Ashton case police said the suspect, Ekkapan Kaewkla, claimed his group was outnumbered during a fight at about 05:00 am on January 1st so he decided to use his homemade gun to protect himself.
Ashton was hit by a stray bullet as he danced on the beach.