For a third person view like this you should create a camera that is at a certain radius from the character while always looking at it and offset in elevation (Z) to look from above basically.
Something similar is shown in the 8 direction billboard example where the camera rotates around the billboard character in the center.
Now when you simply slap 8 direction movement on your character you will get probably undesired results since the character is not moving relative to the perspective (regular third person movement) or depending on where the character is facing (tank controls).
For first person controls (which does not apply here) and tank controls I'm actually using an edited version of the 8 direction behavior called wasd movement which is adjusted to move its object relative to its angle and defaults to w,a,s and d instead arrow keys. Maybe I should share this at some point.
For regular third person movement, which I haven't actually used myself in anything I've created with Baby 3D yet, you should apply vectorX and vectorY of the 8 direction movement behavior relative to the camera angle. Unless I'm totally thinking of something stupid and wrong right now...
If this doesn't help enough I guess I can cook up an actual example in the next few days