How Frustum Culling and Sky Box Working Together ? The skybox appears where it should not appear

When i did frustum culling, far parts of land not rendering. It is good like i want. But after I see sky box instead of these parts. My question is, is this normal ? Or what i need to see or what i need to do ? Because it doesn’t look nice in the game.

I will show my problem to you with pictures. Over “Blender” program.

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