Yes, it is totally safe to eat boiled eggs that have been frozen, however they will likely not taste that great. While it is possible to separate the yolks and whites of a hard-boiled egg, this is not possible with a regular boiled egg. As we have said, egg whites become incredibly unappetizing once they have been frozen as they transform into a rubbery consistency.
So, while it is possible to eat frozen boiled eggs you might want to avoid doing this. You could attempt to remove the cooked egg yolk from the boiled egg, but this is likely to be a messy and unpleasant job. This is why it is probably best to stick to freezing the yolks of hard-boiled eggs rather than soft-boiled eggs.