Travellers being urged to avoid rally sites, stock up on cash, food and water.
Many countries have advised their nationals to stay away from demonstration sites on Monday and ensure that they have enough cash on them, a fully-charged communication device as well as enough food and water to last a while. They have also been advised not to wear red or yellow.
"Participating or showing support in any form to any of the parties is strongly discouraged," the Philippines Embassy in Bangkok said on its website.
"For information, the red and yellow colours are closely identified with some of the parties involved," it said referring to the colours associated with political conflict over recent years.
People who support the Yingluck Shinawatra government have been wearing red, while anti-government groups, who used to wear yellow, have now chosen to wear the national flag along with a whistle.
Meanwhile, the United States Embassy has warned its citizens to be careful, because although mass rallies have been generally peaceful over the past few months, there have still been some deaths and injuries.
"Even demonstrations that are meant to be peaceful can turn confrontational, and escalate into violence without warning," the US Embassy warned.
The People's Democratic Reform Committee plans to set up rally sites at several major intersections in Bangkok and significant areas, namely Asok, Pathum Wan, Lumpini, Victory Monument, R...