Five officers from the holiday island travelled north to nab Shaun Michael Albert Maher, 41, and his girlfriend, Rossarin Phowichai, 25, near her home in Khon Kaen province, where the cassava was supposed to be grown, on Tuesday.
Today the pair were being questioned at Kathu Police Station in Patong about allegations that foreign investors as well as Thais had been ripped off in the ''pay now, profit later'' scheme.
At least 11 cases involving Thais and foreigners have been specified so far, Phuketwan has learned.
At least one Thai family in the Phuket west coast nightlife hub handed over five million baht in payments going back to 2010 but never received any return on their investment.
Allegations of other investors being swindled are being pursued, the Chief Inspector at Kathu Police Station, Colonel Sutthichai Thianpho, said today.
The officers from Patong returned to the island yesterday with Mr Maher and Khun Rossarin. According to police, Mr Maher, whose right leg was in a cast when he was arrested, blamed his girlfriend's aunt for the failure of the scheme.
''The victims have never received any returns,'' Crime Suppression Division's acting chief Colonel Akaradej Pimonsri was quoted as saying.
Cassava has become a popular crop across large tracts of Thailand's farming provinces but so much of it is now being grown that windfall profits are unlikely.