Why is the battery of my 2015 Ford Ranger draining?

It’s very likely that the two lights remaining on inside the car are enough to drain the battery over time. The real question is why a couple of random lights would stay on even when the vehicle is locked up overnight. Initial suspicions would involve the car’s body computer which controls many functions, including interior lighting.

An auto electrician is probably your best bet at this stage. But in the meantime, you can perform an electronic reset by disconnecting the car’s battery overnight. Sometimes this is enough to give the body computer a reality check and will return things to normal. But if it has happened once, it can happen again.