Plumeria seeds generally do not require any complex pre-treatment before planting. However, there are a few simple steps you can take to improve germination rates and encourage healthy growth:

1. Soaking: Soak the seeds in warm water for about 8-12 hours before planting. This helps to soften the seed coat and can speed up germination. Avoid soaking them for too long, as this can cause the seeds to rot.
2. Scarification (Optional): Some gardeners lightly scarify the seeds by gently rubbing them with fine sandpaper or nicking the seed coat with a knife. This process can help water penetrate the seed coat more easily, but it must be done with care to avoid damaging the embryo inside.
3. Warm Environment: Plumeria seeds germinate best in warm conditions. Preparing a warm, stable environment for the seeds can enhance germination. A heat mat can be used to maintain a consistent temperature, ideally between 75-85°F (24-29°C).
4. Good Quality Seed Starting Mix: Use a well-draining, sterile seed starting mix to avoid diseases. Plumeria seeds are prone to rot in overly wet conditions, so a light, airy medium is ideal.

Remember, these steps are not strictly necessary for all Plumeria seeds, but they can be beneficial, especially if you are looking to optimize germination rates and give your seedlings the best start possible.