Albert Barnes Commentary Judges 10:18

"And the people, the princes of Gilead, said one to another, What man is he that will begin to fight against the children of Ammon? he shall be head over all the inhabitants of Gilead." — Judges 10:18 (ASV)

And the people and princes ... - The inhabitants of Gilead appear as a separate and independent community, electing their own chief, without any reference to the West-Jordanic tribes.