The Corrections Department has extended its ban on visits to prisoners for another month, until May 31.
Director-general Narat Svetanan said on Thursday the extension corresponded with the government's extension of the state of emergency for another month to control the spread of coronavirus disease.
Relatives and prisoners could instead communicate through the Line chat app, but relatives must not post online the recordings of the communications. Violators would be banned from online visits, he said.
The chief also said there were no new cases of Covid-19 infection in prisons.
There had been five to date - two prisoners who had already recovered, and three prison officials, one of whom had recovered, he said.