There is a feat named Troll-blooded granting a level 1 human REGENERATION 1 (Dragon Magazine #319).
If you just take a level 1 human with this feat, then get undead (there are many ways for level 1-2, for example in Libris Mortis).
Let's look into MM1 about Regeneration:
Damage dealt to the creature is treated as nonlethal damage.
Now let's look what our undead does (MM1):
Since I don't have the Dragon Magazine #319, could you please check this?