Alleged ponzi-scam couple Wantanee "Mae Manee" Tippaveth and her husband Methee Chinnapha were remanded in custody and taken to Udon Thani prison after making their first appearance in court on Monday.
They were taken from their cell at UdonThani's Muang police station to the provincial court, where police obtained approval to further detain them while their investigation continues.
Ms Wantanee, 29, and Mr Methee, 20, remained tight lipped when approached by the media. Police said they both face further interrogation.
The couple were arrested in Sattahip district of Chon Buri province on Saturday and helicoptered to Udon Thani later that day. Police can detain suspects for 48 hours and then need court approval to further detain them.
There was no application for bail. Their lawyer said the couple's assets had all been frozen so could not be placed as a guarantee. They were taken to Udon Thani prison.
The couple allegedly defrauded people who invested in what has become known as the Mae Manee ponzi scheme, which lured victims with promises of unusually high returns, allegedly up to 93% a month.
The Department of Special Investigation said on Wednesday last week that damage to victims totalled more than 430 million baht, but police had upped the estimate to around 1 billion baht, deputy national police chief Pol Gen Suwat Chaengyotsuk said on Saturday.
The number of victims had risen to more than 3,400 as of Saturday.
The couple face charges of public fraud, public fraud-related borrowing and putting false information into a computer system. They have denied the charges.