The United States embassy is urging all American citizens in Thailand to stock food, water and cash and other essential supplies to prepare for the anti-government protests on Monday.
The advisory, posted on the embassy's website, noted that while protests have been generally peaceful over the last two months, some have resulted in injuries and deaths.
It warned that even demonstrations that are meant to be peaceful can turn confrontational, and can escalate into violence without warning.
"You should avoid areas of demonstrations, and exercise caution if in the vicinity of any large gatherings or protests. Be alert and aware of your surroundings and pay attention to local news and media reports," the advisory said.
"We advise you to plan ahead. It is prudent to ensure you have a week's supply of cash, keep your mobile communications devices charged, and stock a two-week supply of essential items such as food, water and medicine," it added.
Meanwhile, Filipinos travelling to Thailand have been told to avoid displaying any red or yellow items to avoid being caught up in the political unrest, the Philippine embassy in Bangkok said yesterday.
"Participating and/or showing support in any form to any of the parties is strongly discouraged," the mission said in a travel advisory posted on its website.
"For [your] information, the red and yellow colours are closely identified with some of the parties involved," it said in a note directed at Filipinos planning to travel to Thailand as well as those living here.
Yellow and red are highly popular colours in the Philippines, associated with religious festivals in the Catholic country.
And just like here, the hues are rich in historical and political symbolism.
Yellow is the signature colour of supporters of Philippine President Benigno Aquino and his late mother Corazon Aquino.
Red is the campaign colour of his family's arch-political foe, the heirs of the late strongman Ferdinand Marcos.
Marcos' 20-year rule was ended by a bloodless popular revolt by yellow-clad street protesters that propelled the younger Mr Aquino's mother to the presidency in 1986.
The embassy also reiterated an earlier warning by the Philippine Foreign Department for Filipinos to avoid non-essential travel to Bangkok and to steer clear of street protests.
Anti-government protesters have vowed to "shut down" Bangkok from Monday as part of a campaign they have warned could last several weeks.