I have to undo the battery for the hi beams to go off

 

More than likely it's the multi function stalk on your steering column thats bad. The stalk that you pull/push to activate/turn off the high beam.
You have not given any info about your Ranger as to year, but in general the stalk has to be replaced. Not expensive, around $40.00 or so, and fairly easy to do.

 

+1 ^^^

 

In the meantime you could pull the headlights fuse. So you dont have to keep disconnecting the battery. Maybe leave the fuse puller on it so you can pull it or replace it as you need the lights.