Hello Bino,
You can easily compress a whole folder of LAS files (or similarly decompress a whole folder of LAZ files) using either the GUI, the command-line, or the QGIS / ArghGIS "LAStools Pro" toolboxes. In addition you could add the projection information while compressing as this is often missing as shown in the screenshot of the laszip.exe GUI.
simple compression on 8 cores in parallel
laszip -i c:\ISPRS\KRNAP\*.las -odir c:\ISPRS\KRNAP_compressed -olaz -cores 8
simple decompression on 8 cores in parallel
laszip -i c:\ISPRS\KRNAP_compressed\*.laz -odir c:\ISPRS\KRNAP -olas -cores 8
compression on 8 cores in parallel and adding projection info
laszip -i c:\ISPRS\KRNAP\*.las -odir c:\ISPRS\KRNAP_compressed -olaz -utm 33N -vertical_wgs84 -cores 8
compression on 8 cores in parallel and adding projection info and appending spatial indices
laszip -i c:\ISPRS\KRNAP\*.las -odir c:\ISPRS\KRNAP_compressed -olaz -utm 33N -vertical_wgs84 -lax -append -cores 8
Regards,
Martin @rapidlasso