Quoted in the Jakarta Post on Wednesday, Abdul Rahman Saleh, Indonesia's attorney-general, said he had evidence that Tommy opened the account at BNP Paribas shortly after his father resigned as president amid civil unrest in May 1998.
"BNP Paribas assumed the money in the bank was obtained through corruption here," the Post quoted him as saying.
Indonesia's ambassador to the UK, Marty Natalegawa, told Reuters a court in Guernsey had approved the Indonesian government's request to be a third party in the case.
It is expected to outline its position at the next hearing on the case due on March 8.
Tommy, also known as Hutomo Mandala Putra, was freed from prison last year after serving four years for ordering the murder of a judge who convicted him of corruption.
His early release, after serving just a third of his sentence, drew fire from critics who said it showed undue leniency and favouritism for the powerful.
Tommy, like other Suharto children, became one of the country's super-rich businessmen during the rule of his father.
Some of his businesses had been linked to political influence - such as a monopoly on highly lucrative clove distribution and a national car project.
Suharto, who resigned amid demonstrations after more than 30 years of rule, was charged with graft but escaped prosecution as courts accepted medical statements that he was too ill to stand trial.
The former president and his family members deny any wrongdoing.