I don't know how to install LAStools in QGIS 3.0. In QGIS 2.18, you can incorporate it as a provider in Processing -> Options-> Tools for LiDAR data (for example: Installing LAStools in QGIS 2.4?).
But in the QGIS 3.0, you can only find GRASS, GDAL and SAGA in the same place.
Does anyone knows how to install LAStools in QGIS 3.0?