It said unprovoked attacks have been reported in tourist destinations across the country and are particularly common during "Full Moon" parties, other similar events and late at night near bars.
The FCDO advised travellers to "be careful" about taking drinks from strangers or leaving drinks unattended.
"Drink spiking and drug assisted sexual assault have been reported in tourist destinations around Thailand, with both male and female victims," it said in an updated statement.
"Crimes involving guns take place in Thailand, and foreign nationals have sometimes been victims of gun crime."
