The Thai military seized power Tuesday, revoking the constitution and declaring martial law. The coup took place while Prime Minister Thaksin Shinawatra was in New York attending a U.N. General Assembly session.

Thailand has been plagued by a number of military coups since the 1950s. In 1992, prodemocracy demonstrations forced Prime Minister Suchinda Kraprayoon, a former army commander, to resign. Thailand adopted a new constitution incorporating strong democratic principles in 1997 and it was thought the days of military interference in government was over. The latest coup represents a setback for Thai democracy.

Mr. Thaksin, a billionaire-turned-politician who became prime minister in 2001, must shoulder responsibility for creating conditions that led to the coup. His populist promises attracted strong support from the rural population, but urban dwellers resented his autocratic political style, which included installing loyalists in senate seats and attempting to meddle in the personnel affairs of the military to promote his supporters.

The Thaksin family's tax-free sale in January of their 49 percent stake in the family-controlled company Shin Corp., Thailand's largest telecommunications company, to a Singapore firm provoked allegations of corruption and triggered mass demonstrations.

In response, Mr. Thaksin, who won an overwhelming victory in a 2005 election, called a snap election in April. But the opposition boycotted the election and election rules prevented all the parliamentary seats from being filled. Thailand's revered King Bhumibol Adulyadej called the election undemocratic. The constitutional court eventually annulled it and a new election was scheduled to be held in October.

Army Gen. Sondhi Boonyaratkalin said that newly created Council of Administrative Reform carried out the coup to heal mounting rifts in Thai society and to end Mr. Thaksin's undermining of democratic institutions. It is hoped that the military will carry out democratic elections as soon as possible.