They are referring to chronic (long-lasting) influences on acute (immediate) risk of suicide (this is relevant because they're talking about immediate intervention steps to take; if you were interested in epidemiology instead you might instead consider chronic risk of suicide, say over years or decades).
If we were talking about heart health instead, you might say that high blood pressure is a chronic risk for acute myocardial infarction.
Chronic risks they are referring to are found in Table 3, and include "prior attempts, recent hospitalization, living alone, family history of suicide, LBGTQ population, adverse childhood events, stressful life-events, mental illness, physical illness, unemployment, advancing age."
By saying "baseline" I presume they are referring to baseline for that individual. So someone with one or several of these risk factors over a long period would fit into this category: they're at a higher risk than someone without these chronic factors, but at a lower risk than someone with new acute risk factors.