Tower Controller at MGM reported there are no markings delineating the ramp non-movement area from taxiway E1 which could result in vehicles entering an active taxiway without clearance from the Tower.

Narrative

I was working local and CIC (Controller In Charge) with a developmental working ground. Traffic was very light. I noticed an operations vehicle was sitting at the hold bars of runway 21 and E1 and had been sitting there for some time. I asked ground if she was talking to them and she said no. A few minutes later the vehicle called ground on the ground frequency and requested to do a FOD check. Ground gave them permission to move onto runway 3/21 which was ground's control; as well as permission to check Alpha east of runway 3/21.When the operations vehicle got to the hold point of runway 28 and A1 ground switched them to me on local so they could do a runway inspection per our SOP. It was at this point I advised the operations vehicle they should not drive up to the hold bar of runway 21 and E1 without speaking to ground as I believe it poses a safety issue. Adjacent to E1 is both the self-serve fuel depot as well as aircraft hangars. It is possible for a transient aircraft; or an aircraft based on field to want to land on runway 3 and exit onto E1 to get fuel. If an operations vehicle is sitting there without talking to us this could create a safety issue.When I got on break I told my supervisor about this and we started looking into it. According to the Google Maps satellite view there are no movement area hold markings delineating the end of a non-movement area and the beginning of a movement area for E1. If this is accurate then this seems incredibly unsafe to allow a non-movement area to go up to a runway entrance/ exit.E1 needs to become a movement area and movement area hold bars need to be painted to protect E1 and runway 21 from random aircraft/ vehicles from entering it without speaking to ATCT.