Supreme Court Justice Alexandre de Moraes put Bolsonaro under house arrest in a gated community in Brasilia earlier in August after finding the politician had failed to comply with restraining orders meant to stop trial interference.
Bolsonaro faces charges of plotting a coup to overturn his 2022 electoral defeat, and final arguments in the case will begin early in September. He has denied the accusations.
Police reinforcement is "appropriate and necessary" as the next phase of the trial approaches, Moraes said in his decision on Tuesday.
He also pointed to findings in a recent police report as cause for concern that Bolsonaro could try to flee. The police found a draft of a letter from Bolsonaro in 2024 requesting asylum in Argentina, and accused him and his son Eduardo of trying to interfere with the trial.
Eduardo Bolsonaro, a Brazilian congressman now living in the US, has been lobbying in Washington on his father's behalf.
Bolsonaro's lawyers did not immediately respond to a request for comment.
The defence previously said the drafted asylum request did not indicate flight risk, given it was from a year ago, and said Bolsonaro did not breach restraining orders.
Moraes instructed police to avoid disrupting Bolsonaro's daily routine, and not bother his neighbours.
