The holes you can see at Vietnamese cemeteries are former graves.
Yes, the people in that country bury their dear ones twice, the first time shortly after they die, and the second time three years later.
Three years after the death of their relative, the family hire diggers or perform the following grim ritual themselves.
The remains of the deceased are exhumed, usually at night and in the cold season, the remaining flesh is separated from the bones, which are then washed and placed in new caskets to be buried for good this time.
Nobody will blame you for not grieving your dead enough…