Not at this time.
The company did previously have a free Hobby plan but this was deprecated back in March 2024:
https://planetscale.com/blog/planetscale-forever
Currently, all databases created on PlanetScale must be placed on a paid Scaler Pro plan when they are created and will begin to accumulate charges for the time that the database is created.
In order to avoid accumulating additional charges the database would need to be deleted since this then allows the hardware resources needed to keep your database online 24/7 to be turned off.