The Cabinet official in charge of the prime minister's office, Panadda Diskul, said a specially appointed committee has determined that 286.64 billion baht (USD 8.2 billion) in revenues were lost under the scheme, and that former Prime Minister Yingluck Shinawatra is liable for about 200 billion baht (USD 5.8 billion) of the total.
Yingluck was forced from office in May 2014 when a court found her guilty of abuse of power in a personnel case. The army ousted her government shortly afterward.
She is currently on trial for alleged dereliction of duty in administering the program, a criminal charge under which she could be sentenced to 10 years in prison.
Her supporters believe she is being persecuted by the army and by other political opponents of her brother, former Prime Minister Thaksin Shinawatra.
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Thaksin was ousted in a 2006 military coup after demonstrations accused him of corruption, abuse of power and insulting the monarch, King Bhumibol Adulyadej. His ouster set off sometimes-violent battles for power between his supporters and opponents, including the military.
The rice subsidy program was a flagship policy that helped Yingluck's Pheu Thai party win the 2011 general election.
Yingluck has argued it was aimed at helping poor farmers, who were paid about 50 per cent above what they would have received on the world market.
The government evidently hoped it could drive up the world price for rice by warehousing vast supplies, but other producers such as Vietnam took up the slack instead, bumping Thailand from its spot as the world's leading rice exporter.
He said the government would also seek compensation from Yingluck's commerce minister, Boonsong Teriyapirom, and several lower-ranking officials.