An investigation by the National Anti-Corruption Commission found that Boonsong Teriyaphirom and his deputy Poom Sarapol, along with 17 government officials and businessmen, sold rice from the Thai government's stockpile to a Chinese company that did not represent the mainland government.
Commissioner Wicha Mahakhun, who headed the investigation, said the sale which was supposed to take place between the Thai and Chinese governments, caused "serious losses" to Thailand.
The watchdog's announcement comes two days before military-appointed lawmakers will vote on whether to impeach ousted Prime Minister Yingluck Shinawatra, whose government was toppled in a coup last May.
Supporters of Yingluck say the anti-graft commission is backed by the country's conservative establishment, which has ousted several governments allied with Yingluck's brother, former prime minister Thaksin Shinawatra.