This article by Popularmechanics is about options for repairing stripped oil pan drain holes.
But of course, life isn’t easy. The threads in the pan and on the plug are damaged, perhaps from partial cross-threading. What to do now? Forget the drain plug and get a repair kit. A typical kit has a replacement fitting that cuts deeper threads, and when tightened, it seals against a washer and remains in place. Some kits cut fresh, deeper threads for a new plug. A hexhead brass cap with an O-ring seal threads onto the end. When it’s time to change the oil, you unthread the cap. Others (for odd-size, severely damaged holes) are fat, cone-shaped synthetic rubber plugs larger than the drain-plug hole. You force a special rod into an opening in the cone, which temporarily stretches it and reduces its diameter, allowing it to fit in the hole. Withdraw the rod, and the cone relaxes and seals the hole–the cone won’t come out until you force in that rod to stretch it.
If the drain plug looks marginal, consider installing a Fram oil-drain valve kit. These are available for the most common types of drain-plug holes. Thread a spring-loaded valve assembly with a copper washer into the hole and tighten. The valve is the primary oil seal, and a knurled cap threads on fingertight against an O-ring–this keeps out dirt.
When it’s time to drain oil, unthread the cap and thread on a fitting with a drain hose, which you can aim right into the pan (no splatter and no hot oil running down your arm). The hose fitting has an internal tip that pushes open the spring-loaded valve, and the oil drains out. When the pan is drained, unthread the hose fitting (the valve springs shut), reinstall the fingertight cap and you’re good to go (after changing the filter and putting fresh oil in the engine, of course). If the drain plug is okay and you want to reuse it, replace the washer and then tighten the plug to specifications–20 ft.-lb. to perhaps 35 ft.-lb.–depending on the size of the plug.
Hope this helps!