The BBC's Burmese-language service cited sources on Thursday as saying the Nobel laureate was now being held in a separate building inside the jail.
It said the she had been moved from house arrest to solitary confinement in a prison in the capital Nay Pyi Taw.
The 77-year-old has been charged with at least 20 criminal offences since she was toppled in a military coup in February 2021, including multiple counts of corruption.
Reuters could not reach Suu Kyi or her representatives for comment. Her lawyers have been barred from speaking about her cases.
A spokesperson for the junta did not respond to requests for comment.