Bail is revoked by a judge usually on a request from either an assistant district attorney of from the county's bail agency or pretrial services. Both examples are almost certainly going to lead to at least a modification (increase) in bail. I'd love to hear some elaboration on the comment the questioner posted concerning what appears to be a direct communication from the DA threatening revocation of bail unless a guilty plea was tendered. Are you unrepresented? If so, you need counsel immediately. If you can't afford privately retained representation, apply with the Public Defender.
Either situation can cause bail to be revoked. It is the DA that would request or file a motion to revoke bail. It is ultimately up to the Judge and they have a lot of discretion.
Michael l. Doyle