Sinon, essaie en rajoutant un select en colonne:
SELECT
rech.*,
requis.Id_rech,
requis.nom AS "Nom_statut",
(SELECT id_niveau FROM recherche_niveau WHERE id_recherche=rech.id_rech) AS "Niveau joueur"
FROM recherche rech, recherche requis
WHERE
requis.Id_rech=rech.Recherche_requis_id
AND rech.Type=3
AND rech.Iso_pays ="'.$_SESSION['Iso_pays'].'"
ORDER BY nom