Most "classic" scary movies people tend to suggest are not very scary by modern standards, which may make them well suited for your son.
Fatal Attraction... (may not be age appropriate, but the bunny scene... scary AF). I think 'The Ring' was one of the first scary movies I saw in theaters and I was around his age; not traumatizing, but actually suspenseful unlike most horror films these days. More recent recommendations include 'Get Out' (great movie) and 'The Invisible Man' (solid option).
When I was 5, Hocus Pocus was scary, but alas...