The decision, which must be endorsed by the Constitutional Court to take effect, came soon after Thailand's influential army chief appeared to back the protesters call, saying new elections might be needed to resolve the country's political crisis. The standoff descended into the deadliest political clashes in nearly two decades on Saturday, when 21 people died in clashes.
Prime Minister Abhisit Vejjajiva, who was largely seen as having the backing of the powerful military, has remained defiant in his refusal to resign. But the about-face of the head of the army, which has not hesitated to stage coups during previous political instability, puts Abhisit under unprecedented pressure.
"If the issue cannot be resolved through political means, then Parliament dissolution seems to be a reasonable step ... I just want peace to prevail," army chief Gen. Anupong Paochinda told reporters. Parliament's dissolution is a necessary step for new elections.
"Right now the circumstances dictate that a solution should be achieved through political means," he said.
The latest turmoil is part of a yearslong struggle for power, pitting the rural supporters of ousted Prime Minister Thaksin Shinawatra against members of the country's traditional ruling elite, which includes business leaders, the military brass and bureaucrats - supported by the urban middle class.
Thailand has seen three governments in the four years since a coup drove Thaksin from power in 2006. Protesters have taken to the streets each time their rivals came to power.
In 2008, anti-Thaksin protesters besieged the government headquarters for months and occupied the airports for a week. The crisis was defused by a court ruling similar to Monday's that unseated the pro-Thaksin government. Subsequently, Abhisit became prime minister.
The repeated unrest has threatened to ruin the country's reputation as a stable haven for commerce, investment and tourism.
Monday's ruling could set the stage for another change in power. But it is unlikely to be the last word. It could offer a way out of the political deadlock between Abhisit's government and the Red Shirts, or it could fuel another round of counter-demonstrations by government supporters.
The Election Commission found the Democrat Party - Thailand's oldest - guilty of misusing campaign donations. No date was set for the Constitutional Court to hear the case.
Raucous cheers erupted at a major protest site when a speaker announced the decision to his audience.
"This is a victory for us. Our democracy heroes didn't die in vain," Veera Musikapong, a protest leader, said.
The Election commission was ruling on a complaint filed by the Red Shirts that the Democrat Party received more than 258 million baht ($8 million) in donations from a private cement company, TPI Polene, without declaring it, as required by law, and used it for election campaigning. The party was also accused of misusing 29 million baht ($800,000) from a political fund.
The commission had scheduled the ruling for April 20, but announced it more than a week early without explanation. It came on the eve of a four-day holiday for Songkran, the traditional new year when many urban Thais visit relatives in the countryside. Many people had feared that the festival - where people douse friends and strangers alike with water - would be marred by the political unrest and demonstrations.
If the party is dissolved, new elections would have to be called, and the prime minister and all the top executives of the party would be barred from politics for five years.
Unconfirmed reports in local newspapers have also said that Abhisit's coalition partners in the government want him to compromise with the protesters by dissolving Parliament in the next six months instead of by year's end, as he had earlier proposed. He must call elections by the end of 2011.
With the government under pressure, the Red Shirts struck a defiant tone Monday, parading coffins carrying slain protesters through the capital and saying they would not back down.
"Our position is clear. We want the Parliament dissolved now. The only way to solve this political impasse is for Parliament to be dissolve and new elections called," said Weng Tojirakarn, a Red Shirt leader.
The procession started at Phan Fa Bridge, located in the historic section of Bangkok that serves as one of the protesters' two bases. It then drove through the modern commercial heart of the city.
"These are the heroes of democracy," another protest leader shouted from a loudspeaker mounted atop a truck in the motorcade.
On Saturday, four soldiers and 17 civilians, including a Thomson Reuters cameraman, died in the clashes. More than 800 were wounded. Many of them were shot with live ammunition but it remains unclear who did the shooting. Each side accuses the other.
Government spokesman Panitan Wattanyagorn said the military was under orders to fire live ammunition either into the air or in self-defense.
Autopsies on 11 bodies found that nine died of gunshot wounds and one from heart attack. The 11th was the Reuters cameraman, whose relatives asked that the results not be disclosed.
The unrest has shaken the country's economy, and stocks closed 3.6 percent down on Monday.