A majority of the nine judges ruled to hand down a 12-year prison term to Pracha and a 10-year term to Pol Maj Gen Athilak Tanchukiat, former director of the Public Disaster Prevention Office, for their roles in the 6.687-billion-baht procurement deal.
Pracha is the fourth political office holder to be slapped with a jail sentence by the court - after former public health minister Rakkiat Sukthana, ousted prime minister Thaksin Shinawatra and former deputy interior minister Vatana Asavahame.
Rakkiat, a former Democrat public health minister, is serving a 15-year jail sentence for corruption, handed down in 2003.
Vatana fled, apparently to Cambodia, after being sentenced in 2008 to 10 years for corruption in the Klong Dan waste water treatment project scandal. Thaksin, also sentenced in 2008, has a residence in Dubai, although he travels frequently. Like Pracha, Vatana and Thaksin were convicted and sentenced in absenti after ignoring several court orders to appear in person.
The Supreme Court issued a warrant for the arrest of Pracha, who missed the reading of the verdict for the second time Tuesday. Pracha was reported to have fled overseas.
A warrant was also issued for the arrest of Pol Maj Gen Athilak who did not show up at the court Tuesday.
Former Bangkok governor Apirak Kosayodhin, former interior minister Pokin Polakul and former commerce minister Watana Muangsook were cleared of wrongdoing because of a lack of evidence. All of them turned up at the court.
The charges against Steyr-Daimler-Puch Spezialfahrzeug AG, the Austrian supplier, were temporarily dismissed.
The case was brought before the Supreme Court in 2011 by the National Anti-Corruption Commission (NACC), which accused the five individuals and the supplier of malfeasance and price collusion over the purchase of 315 fire trucks and 30 fire boats.
According to the NACC, the procurement was overpriced and benefited the Austrian supplier, and Pracha and Pol Maj Gen Athilak failed to compare the prices with those of the same types of locally manufactured and distributed equipment.
The purchase contract was signed by late Bangkok governor Samak Sundaravej, while his successor, Mr Apirak, signed a letter of credit for the contract, committing City Hall to begin paying the supplier.
The four men, along with the Austrian supplier, were accused of corruptly arranging the deal, which was found by the anti-graft agency to be highly overpriced.
Mr Apirak was forced to step down as the city governor when the NACC decided on the indictment.
He thanked the court Tuesday for granting him justice.
Mr Apirak declined to discuss his political future after being cleared of wrongdoing.
"I'm not thinking about it now," he said.
Bangkok governor MR Sukhumbhand Paribatra declined to discuss the case Tuesday out of concerns it might affect the ongoing dispute between City Hall and the fire vehicle supplier.
The Bangkok Metropolitan Administration (BMA) brought the case to the Geneva-based Court of Conciliation and Arbitration in its attempt to cancel the contract in 2010. MR Sukhumbhand said the BMA will send the Supreme Court's ruling to the international court of arbitration for consideration.
A source at the BMA said Tuesday that City Hall's argument is that collaboration between insiders and outsiders has caused damage to the BMA, which cannot make use of the vehicles due to the legal complications.
The BMA has already filed a lawsuit with the Civil Court against those involved in the scandal, the source said.
Another source at the BMA said although City Hall has already made payments to the supplier, it has not taken possession of the fire vehicles.
All 315 fire trucks and 30 fire boats have remained at Laem Chabang port in Chon Buri and a warehouse in Nonthaburi's Sai Noi district.
The source said the BMA's committee, set up to determine who should be responsible for the damage, had decided on six people. They are Mr Pokin, Pracha, Mr Watana, Pol Maj Gen Athilak, Samak and Mr Apirak.
The report was submitted to the Finance Ministry which later decided to hold Khunying Nathanon Thaveesin, former city clerk, responsible for the damage.
The six lodged a complaint against the decision with the Administrative Court. It is expected that Mr Pokin, Mr Watana and Mr Apirak will use the Supreme Court's ruling to fight the case.
Nam Yimyaem, a former investigator in the fire vehicle scandal, said Tuesday the case should be a lesson for political office holders and state officials.
He said the scheme has done enormous damage to the BMA.
"The damage is huge. The fire vehicles are being left to rust as the case is processed. Any deal should be straightforward and transparent," he said.