Finance Minister Sommai Phasee has instructed the Comptroller-General's Department to outline how to seek compensation from ousted prime minister Yingluck Shinawatra for estimated damage of more than 500 billion baht from the rice-pledging scheme.
The Finance Ministry must file a civil suit demanding the return of government money following a request from the National Anti-Corruption Commission (NACC), he said.
Several state agencies have been involved in the issue since it is a landmark case, Mr Sommai said.
"As it's a big issue, I need to discuss it with related units before answering any questions," he said.
"We cannot do it briskly — it needs thorough consideration. It'll take a few days to see how we can do that."
The NACC recently said it would recommend the ministry lodge a civil suit demanding compensation from Ms Yingluck over negligence in her government's rice scheme.
The move came after the NACC advised the ministry to proceed with a civil lawsuit against 21 individuals and companies involved in allegedly corrupt government-to-government rice deals. They include former commerce minister Boonsong Teriyapirom, his deputy Poom Sarapol, 19 other high-level officials, private sector executives and two companies.
The NACC has already filed a lawsuit with the Office of the Attorney-General accusing Ms Yingluck of dereliction of duty for failing to stop losses and corruption in the rice subsidy programme.
Mr Sommai said finance permanent secretary Rungson Sriworasat was in charge of estimating losses from the scheme.
A ministry subcommittee overseeing accounting of all rice subsidy schemes earlier estimated losses from buying 84 million tonnes of paddy rice in the 15 schemes from 2004-14 amounted to 682 billion baht, with the Yingluck government alone accounting for 518 billion. The subcommittee is led by Mr Rungson.
Mr Rungson said the subcommittee would meet next Wednesday to update members on accounts to the end of fiscal 2014 from the latest data. The fiscal year runs from Oct 1 to Sept 30.
The latest estimate of financial losses has already taken depreciation of rice in stockpiles into account, he said.
The estimate is based on 10% depreciation in the second year, 20% in the third year and a maximum 40% in the fourth year. Depreciation is allowed to be recorded in the first four years.
A recent inspection of the 17 million tonnes of milled rice bought under the previous government's scheme found only 2.19 million tonnes were of standard quality and classified as Grade A rice.
Some 14.4 million tonnes were judged to be substandard or Grade B, while the rest was classified as Grade C because it was either rotten or had been registered incorrectly.
The inspection was done by a team working for PM’s Office Minister ML Panadda Diskul.
Mr Rungson said the Commerce Ministry's rice sale prices needed to be considered in the loss estimate. The ministry had managed to sell rice in recent lots at higher prices than rice sold before the coup last May 22.
The government this week agreed to sell 496,243 tonnes worth 7.85 billion baht to 38 winning bidders in the first auction of state rice stocks this year.
The auction fetched 11 baht a kilogramme on average for white rice, with the offer prices for Hom Mali reaching 31 baht per kg.