can anyone tell me the minimum thickness allowed for front disc rotors. i have a 69 beetle and the drivers side has a slight warp but the rotors dont look very thick.

Its 8.5 mm

If they don't look all that juicy, and one of them has a warp, replace them. They aren't the most expensive things in the world.
Sometimes, by the time the warp is machined out of them, they are outside tolerance for thickness. Also, when they warp, it means the whole grain of the metal bends, and they will probably warp again.

There's nothing nicer than a pair of new discs on a shaky beetle. Trust me, I have an S