The Department of Corrections says Monta "Ying Kai" Yokrattanakan, accused by former employees of lodging false theft complaints against them, is ill, but denies rumours she has died in authorities' custody.
Patikhom Wongsuwon, the department chief, said Wednesday Ms Monta may have come down with a mild illness, but said the prison where she was being held is happy to treat her.
Ms Monta is facing charges of making false complaints to police, attempted human trafficking and insulting the royal institution. She is being detained at the Central Women's Correctional Institute in Bang Khen.
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The Metropolitan Police Bureau (MPB) is probing some investigators at Pracha Chuen police station, who handled Ms Monta's complaints against her employees on theft charges.
MPB deputy chief Jaruwat Waisaya said irregularities were found in police reports involving Ms Monta's nine complaints. About 10 officers at the station may have embellished details of the investigation against the former employees, he said.
The former station chief is likely to be probed as well because he endorsed the reports, according to Pol Maj Gen Jaruwat.
Meanwhile, the Crime Suppression Division (CSD) is looking into the background of Ms Monta whose civil registration record does not appear to show who her parents were.
She also has changed her first and family names twice, which makes it harder for officers to trace her background, a CSD source said.
The probe has found she has less than 100,000 baht in her nine bank accounts, which is at odds with suggestions she is rich. Ms Kai complained an employee stole 400 baht weight gold bars from her.
The Economic Crime Suppression Division is examining where Ms Monta draws her income and whether she has run other businesses apart from a car wash.