Lac Khmer is the natural dyeing thing that Khmer people use it in dyeing and old traditional wedding ceremony. Some province, they have followed the traditional ceremony of grinding Lac Khmer in their wedding ceremony.
Weaver used Lac Khmer to dye red. These are the process of weaver use Lac Khmer to dye cotton yarn. She ground them to small pieces and boiled it to get dyed water. You can follow the process of dyeing in images below: