BANGKOK – A bomb blast killed an anti-government protester and wounded 22 at Bangkok’s blockaded Don Muang airport on Tuesday, hours before a vote fraud case that could deal a crippling blow to the government.

Channel 7 television said an M79 grenade was fired from a flyover near the domestic airport, which has been occupied by the People’s Alliance for Democracy since last Thursday, part of the escalating campaign to topple the six-party ruling coalition.

An emergency services official said 17 of the wounded in the blast, which occurred shortly after midnight, had already been discharged from hospital.

Hundreds of red-shirted government supporters surrounded the Constitutional Court in Bangkok, where judges were due to begin a final hearing on the vote fraud case at 9:30 a.m. (0230 GMT).

“We are here to stop the judges from holding their hearing,” Thai television quoted a protest leader as saying outside the court compound, where scores of riot police guarded the building.

Channel 3 TV said the hearing would be moved to another court in the city, but the report could not be confirmed.

The Constitutional Court has moved with uncharacteristic speed to wrap up a case that could dissolve the elected government. Its ruling could come as early as Wednesday.

The court is widely expected to order the disbanding of Prime Minister Somchai Wongsawat’s People Power Party (PPP) and two coalition partners.

If it does, Somchai and other leaders would be barred from politics and many cabinet ministers would have to step down. The PPP’s dissolution, however, will not necessarily mean a snap election as many MPs will simply switch to a new “shell” party.

The yellow-shirted demonstrators are trying to topple Somchai, whom they accuse of being a pawn for his brother-in-law, former premier Thaksin Shinawatra. Thaksin was ousted in a 2006 coup and is now in exile.

Somchai insisted on Monday he would not go.

“I will not quit and I will not dissolve parliament,” he told reporters in the northern city of Chiang Mai.

The PAD protesters were due to end a three-month occupation of the prime minister’s office on Tuesday to consolidate their grip on the international airport, which has been blockaded for a week, adding to the pain of a tourist- and export-dependent economy already suffering from the global financial crisis.

Finance Minister Suchart Thada-Thamrongvech told Reuters on Monday the economy might be flat next year, or grow by just 1-2 percent, after earlier growth forecasts of between 4-5 percent.

Thailand’s Board of Trade director said the cost of the airport closures was “incalculable,” but a senior board member offered a figure, telling the Nation newspaper lost export earnings ran at around 3 billion baht ($85 million) a day.

The air cargo industry has ground to a halt, while the city’s main domestic hub, Don Muang, has also been occupied for five days.

Rating agency S&P cut Thailand’s outlook to negative from stable, saying there was a possibility of widespread violence.

The chaos has worried Thailand’s neighbors, due to meet in the country in two weeks for a regional summit. The Thai cabinet is expected to approve a delay to March at their Tuesday meeting.