Answer by Leeft for THREE.js check if object is in frustum

Your code is using

frustum.setFromMatrix( camera.projectionMatrix );

But that isn't the matrix you want. Instead use:

frustum.setFromMatrix( new THREE.Matrix4().multiplyMatrices( camera.projectionMatrix, camera.matrixWorldInverse ) );

as answered in How to determine if plane is in Three.js camera Frustum