About 1,000 of the red-clad United Front for Democracy against Dictatorship (UDD) began to gather at the Democracy Monument in Bangkok on Sunday in order to commemorate 80 years of the country's democracy.

The rally was originally scheduled to begin at noon and continue until midnight.

Traffic around the monument was extremely congested and the police planned to block the roads nearby. Motorists were suggested to avoid routes surrounding the gathering venue.

Metropolitan Police has already deployed about 600 police officers to maintain law and order as some 50,000 Red-Shirt supporters were expected to join the rally.

Thailand had been a kingdom under absolute monarchy for over seven centuries until the country changed into constitutional democracy in June 1932.