In rLiDAR, you can segment trees by using CHMs ASCIIs produced by Fusion. Can the same be done in lidR? I know in lidR you have to use the .laz file for tree segmentation:

LASfile <- system.file("extdata", "MixedConifer.laz", package="lidR")
las <- readLAS(LASfile, select = "xyz", filter = "-drop_z_below 0")
# Using Li et al. (2012)
las <- segment_trees(las, li2012(R = 3, speed_up = 5))

So basically, instead of using the .laz file, can I just use its representative CHM.asc produced by Fusion to segment/find trees and then make convex hulls. The reason for using lidR is that I have done crown delineation using rLiDAR, but since rLiDAR does not use more than one CPU cores, it takes a lot of time. However, lidR does support parallelization, hence it's way faster than rLiDAR.