How to properly rig the shoulder of this low poly model? How to properly rig the shoulder of this low poly model?
Have tweaked weights, but didn't get desired results. Is there any other problem?
Edit: Link to File: https://pasteall.org/blend/b5a93745a9f44db79dc5ed6a48179b92

By desired results, I meant that the area below the arms is also getting distorted, which I didnt want. Is there any problem in the mesh itself?

Thanks
You need to :

Go in Edit mode, some normals are flipped, recalculate them
Add some edge loops so that your armature is able to bend the object:



Reparent With Automatic Weight
Bring some corrections in Weight Paint mode