The warning was a response to a week of near-nightly riots, during which mosques and migrant-related facilities were attacked by anti-immigrant mobs, reports the Bangkok Post.
It was issued specifically in regard to anti-racism counter-demonstrations planned for Wednesday (Aug 7), which British authorities feared might draw a violent response from far-right groups.
However, the rallies passed off almost entirely peacefully, after police flooded the streets of numerous English towns and cities and reiterated that violence by suspected far-right agitators would not be tolerated.
The earlier violence was provoked by misinformation spread on social media about the suspected perpetrator of a knife attack on July 29 that killed three children in Southport.
The Thai embassy advised against travelling to some cities, including Liverpool, Bristol, Manchester, Stoke-on-Trent, Blackpool, Belfast and Hull.
Thai nationals can contact the embassy at +44 (0) 791 8651720 or via email for information or in case of an emergency.