Albert Barnes Commentary 1 Kings 22:47

"And there was no king in Edom: a deputy was king." — 1 Kings 22:47 (ASV)

In the time of Solomon, Hadad reigned over Edom, according to the Septuagint (1 Kings 11:14). It appears from the present passage that the country had been subdued again, either by Jehoshaphat or an earlier king, and was dependent on the kingdom of Judah. It was governed by a “deputy” or viceroy who, however, was allowed the royal title (compare 2 Kings 3:9, 2 Kings 3:12, and 2 Kings 3:26). This method of governing dependencies through subject-kings was an almost universal practice in the East until the time of Cyrus (see the note on 1 Kings 4:21).