check gas cap light keeps coming on 300 miles on 2002 Ford Ranger

changed gas cap several times. reset engine keeps repetting after several 100 miles.

2 answers
Could it be another evaporative emission control system problem, masking itself as a gas cap problem? Is the gas cap sealing area on the filler neck un damaged?
Try replacing your gas cap with a new dealer gas cap, not an after market one. It should help this situation.