Hi,
You need to just add an attribute to enable labels to be visible always on the map by adding below ode within addMarkers( ).
labelOptions = labelOptions(noHide = T)
Example-
leaflet() %>% addTiles() %>% addCircleMarkers(lng=77.6944, lat=12.9811,label = "My Office",color = "red",labelOptions = labelOptions(noHide = T))
You can also add CSS to change the font size, direction, styling using style attribute within labeloptions( ).
Hope it helps!