Large Grub in a Dead Tree Branch in Thailand: Likely a Longhorn Beetle Larva

A 3-inch white grub with a brown head was found in a ½-inch bore hole in a dying branch. The expert identified it as a cerambycid (longhorn beetle) larva—a diverse family of wood-borers. Crucially, the beetle likely didn't kill the branch; it colonized wood already stressed or dead from other causes (disease, drought, lightning).

Search "Cerambycidae" for images and life history. No control needed for the tree; focus on overall tree health. If the tree is valuable, consult a local arborist for the primary decline cause.