It also urged all to check the embassy's web page and Twitter feed for updates.
"Even demonstrations that are meant to be peaceful can turn confrontational and escalate into violence. You should avoid areas of demonstrations, and exercise caution if in the vicinity of any large gatherings, protests, or demonstrations. Be alert and aware of your surroundings and pay attention to local news media reports."
(Full announcement: http://bangkok.usembassy.gov/service.html)