It wouldn't be over stocked but they are incompatible fish. Neon tetras are known fin nippers and can cause a lot of stress to the betta. Even if they don't bother the betta right away doesn't mean they won't. What are your thoughts BigManAquatics ?
I have some baby java fern plants and plenty of duckweed and frogbite.
1. Mini java fern $2.00 a piece
2. Duck weed $1.00 per tablespoon.
3. Frogbite $1.00 per plan
4. Hornwort $5.00 a plant pencil long.