The Office of the Auditor-General (OAG) has proposed filing a petition to the Supreme Administrative Court asking it to reconsider the Klong Dan wastewater treatment case in which the court ruled the government must pay almost 10 billion baht in compensation to the project contractor.

"The OAG offers itself as a representative to file the petition if the Finance Ministry hesitates to do so," Auditor-General Pisit Leelavachiropas said.

If the Finance Ministry, which is overseeing the payment of 9.8 billion baht to the NVPSKG consortium, cannot take action itself, the OAG is ready to ask the court for fair treatment, he said.

The offer is to make sure the government will not pay a kha ngo (stupidity payment), or punitive compensation.

In 2014, the Supreme Administrative Court ordered the Pollution Control Department (PCD) to compensate NVPSKG after it was found guilty of scrapping the consortium's construction contract unlawfully when the wastewater treatment plant was nearly finished.

The PCD signed the contract in 1997 to hire NVPSKG to build the plant in Samut Prakan's seaside district of Bang Bo, but it later decided to scrap the contract after finding the project was mired with irregularities including illegal land acquisition.

Former deputy interior minister Vatana Asavahame was found guilty of malfeasance by the Supreme Court's Criminal Division for Political Office-Holders in relation to the land deal in 2008.

Despite the wrongdoing, the PCD decided to pay the compensation and the first tranche of 3.2 billion baht and US$ 21.7 million (765.31 million baht) were paid last November.

However, the Anti-Money Laundering Office (Amlo) last week questioned the contractor's rights to claim the compensation amid suspicions that NVPSKG was involved in corruption in the project.

This resulted in the suspension of the second tranche payment worth 4.7 billion baht scheduled for May 21.

According to acting Amlo secretary-general Seehanat Prayoonrat, the consortium, together with other parties, were involved in illegal occupation of the public land used for the project and received benefits from such illegal activities.

Mr Pisit said an initial inspection found some "traces of irregularities" involving NVPSKG in previous court verdicts on the project.

These can serve as new evidence which the government can use to back a fresh appeal, said the auditor-general.

"I've informed Prime Minister Prayut Chan-o-cha of the OAG proposal," he said, adding Finance Minister Apisak Tantivorawong was also told of the legal move.

However, Deputy Prime Minister Wissanu Krea-ngam said it is too soon for the government to say whether it backs the OAG move.

The government has to follow the law and will not make any comment that can mislead people into believing it will not pay the compensation.

"Let the OAG discuss the matter further first," Mr Wissanu said, adding a person has a right to ask the court to reconsider a legal dispute if he discovers evidence to back his petition.