The person in charge of the Senate Bureau of Intelligence, referred to as either the Director of the Senate Bureau of Intelligence or the Director-General of the Senate Bureau of Intelligence, oversaw the entire organization. This organization, the SBI, belonged to the Galactic Republic Senate, and operated independently from the Republic Intelligence, which was the intelligence arm of the military.
Armand Isard occupied this role leading up to and throughout the Clone Wars, concurrently serving as the Director of Republic Intelligence.
Furthermore, the Bureau included the position of assistant director, in addition to that of Director.