There’s many different ceremonies involved in Khmer weddings, one of which is the knot tying ceremony. Close family and friends are to tie these blessed strings around the couple’s wrist while the couple hold a sword. The sword is there because at the marriage of the first Khmer prince he had a sword and used it to protect him and the bride from a suitor. Now the sword is there to symbolize that the groom will protect the bride.
My funniest uncle cracked a joke about how the sword doesn’t fit anymore and that we should just use a gold plated AK-47 instead of a sword. Lmfao