Input: [{:province :a, :district :b, :amphoe :c}, {:province :a, :district :k, :amphoe :g}], Output: {:a {:c [:b], :g [:k]}}

group_address.clj

(defn group-amphoes [locations]
   (->> locations
        (group-by :amphoe)
        (map (juxt first (comp #(mapv :district %) second)))
        (into {})))
        
(defn group-provinces [locations]
   (->> locations
        (group-by :province)
        (map (juxt first (comp group-amphoes second)))
        (into {})))
        
(group-provinces [{:province :a, :district :b, :amphoe :c}, {:province :a, :district :k, :amphoe :g}])
;=>  {:a {:c [:b], :g [:k]}}