Hawaiian law requires at least one spouse to have lived in the state of Hawaii for at least six months before filing the Complaint for Divorce. It seems unlikely that your friend would be able to meet that requirement and then pursue a divorce in Hawaii if he is present on a six month (tourist?) visa. If his wife remains in Tonga, that also complicates things - the Hawaiian court won't have personal jurisdiction over the wife, and won't have jurisdiction to divide property which is located in Tonga. Thus, it would probably be best if he divorced in Tonga.