Thailand had a turbulent political history even before Tuesday`s declaration of martial law, with at least 18 successful or attempted coups.
Here are some significant dates in Thailand`s political history:
June 24, 1932: King Prajadhipok falls in a bloodless coup. A constitutional monarchy and parliament are introduced.
December 1938: Military leader Luang Phibun Songkram becomes prime minister.
June 9, 1946: King Rama VIII dies under mysterious circumstances. His brother Bhumibol Adulyadej assumes the throne.
November 8, 1947: Another coup leads to Phibun`s return to power, ushering in a new period of military rule that lasts until 1973.
October 14, 1973: Some 400,000 student-led protesters topple the military rulers, leading to a brief flowering of democracy.
October 6, 1976: A bloody crackdown on student protesters ends with the military returning to power.
March 1980: Moderate military ruler Prem Tinsulanond survives several coup attempts and opens politics to some popular participation.
July 1988: General Chatichai Choonhavan wins general elections and the country enters an economic boom.
February 1991: General Sunthorn Kongsompong stages a coup and topples Chatichai`s civilian government. He sets up a junta, the so-called National Peace Keeping Council, to govern.
May 1992: Hundreds of thousands of pro-democracy protesters fill the streets of Bangkok demanding a return to civilian rule. Dozens are killed after junta member General Suchinda Kraprayoon assumes the prime minister`s post without contesting elections.
The king summons the generals and pro-democracy leaders to the palace, admonishes them and asks them to reconcile. The killings stop and Suchinda agrees to resign.
September 23, 1992: Democrats party leader Chuan Leekpai is voted prime minister, ending months of instability.
July 2, 1997: Thailand devalues the baht, triggering the Asian economic crisis.
October 11, 1997: The king signs the country`s 16th "People`s Constitution" into law, in a major development for political reform and democracy.
January 6, 2001: Telecom magnate Thaksin Shinawatra wins elections to become the 23rd prime minister.
January 5, 2005: Thaksin`s government becomes the first elected civilian administration to complete a four-year term. His Thai Rak Thai party is re-elected a month later.
February 24, 2006: Under increasing calls to quit over a telecoms corruption scandal, Thaksin dissolves parliament and calls new elections.
April 2, 2006: Voters go to the polls. Thaksin`s apparent victory is undermined by a strong protest vote and a boycott by main opposition parties.
September 19, 2006: Thailand`s armed forces oust Thaksin in a bloodless coup and impose martial law.
December 23, 2007: People Power Party, comprising Thaksin`s allies, wins elections and goes on to form a coalition government.
May 2008: Royalist anti-Thaksin "Yellow Shirts" relaunch street protests that precipitated the 2006 coup.
September 2008: State of emergency declared after clashes between pro- and anti-government groups that left one person dead and dozens wounded.
Constitutional Court strips Thaksin-allied premier Samak Sundaravej of his powers, ruling he illegally accepted payments for hosting TV cooking shows. Thaksin`s brother-in-law Somchai Wongsawat takes his place.
October 2008: Clashes between police and demonstrators leave two people dead and nearly 500 wounded. Court sentences Thaksin in absentia to two years in jail for corruption after he flees the country.
November-December: Thousands of Yellow Shirts blockade Bangkok`s airports. State of emergency imposed for nearly two weeks.
December: Constitutional Court dissolves Somchai`s party, forcing him from office. British-born Abhisit Vejjajiva of the Democrats becomes premier in a parliamentary vote with army backing.
January-March 2009: "Red Shirts" loyal to Thaksin stage mass protests in the capital against Abhisit`s government.
April 2009: Red Shirts storm an Asian summit in the beach resort of Pattaya, forcing the evacuation of regional leaders. Riots and a 12-day state of emergency in Bangkok ensue, leaving two people dead.
March 2010: Tens of thousands of Red Shirts begin rolling demonstrations calling for Abhisit`s government to step down, saying it is elitist and undemocratic.
April-May 2010: Street clashes between Red Shirt protesters and armed troops leave more than 90 people dead, mostly civilians, in the country`s worst civil unrest in decades.
July 3, 2011: Thaksin`s allies sweep to power in elections on a wave of support from their Red Shirt followers.
August 2011: Parliament elects Thaksin`s youngest sister Yingluck Shinawatra as Thailand`s first female prime minister.
November 2012: Police fire tear gas at demonstrators as clashes erupt at the first major street protests against Yingluck`s government.
November 2013: Opposition protesters occupy the finance and foreign ministries demanding Yingluck resign.
December 2013: Police use water cannon and tear gas on protesters who storm the government and police headquarters. Opposition lawmakers resign en masse from parliament.
Yingluck calls early elections as demonstrators return to the streets. Opposition announces a poll boycott.
February 2, 2014: Opposition demonstrators prevent 10,000 polling stations from opening for the election, affecting several million people.
March 21, 2014: Constitutional Court annuls February elections.
April 30: Government announces new elections for July 20.
May 7: Constitutional Court removes Yingluck and several cabinet ministers from office.
New caretaker premier Niwattumrong Boonsongpaisan appointed by remainder of cabinet.
May 15: The Election Commission says a general election scheduled for July 20 is "no longer possible" as polls cannot be held without the support of the protesters.
May 20: Army declares martial law, stressing the move "is not a coup".