diff --git a/src/controllers/ApiWebServiceController.ts b/src/controllers/ApiWebServiceController.ts
index 69781172..e47c145c 100644
--- a/src/controllers/ApiWebServiceController.ts
+++ b/src/controllers/ApiWebServiceController.ts
@@ -607,18 +607,28 @@ export class ApiWebServiceController extends Controller {
     }
 
     // join กับ posMaster/employeePosMaster/employeeTempPosMaster เพื่อกรองตามสิทธิ์การเข้าถึง
+    // Skip duplicate join - posMaster already joined for registry systems at lines 569-571
+    // Permission condition will use the existing alias
+    const posMasterAlreadyJoined = (system === "registry" || system === "registry_emp" || system === "registry_temp") && tbMain === "Profile";
+
     if ((tbMain === "Profile" || tbMain === "ProfileEmployee") && posMasterCondition !== "1=1") {
       if (tbMain === "Profile") {
-        queryBuilder.innerJoin("Profile.current_holders", "posMaster", "posMaster.orgRevisionId = :currentRevisionIdPerm");
-        queryBuilder.setParameter("currentRevisionIdPerm", this.currentRevisionId);
-      } else if (tbMain === "ProfileEmployee") {
-        // Use the correct relation based on posMasterAlias
-        if (posMasterAlias === "employeeTempPosMaster") {
-          queryBuilder.innerJoin("ProfileEmployee.current_holderTemps", "employeeTempPosMaster", "employeeTempPosMaster.orgRevisionId = :currentRevisionIdPerm");
-        } else {
-          queryBuilder.innerJoin("ProfileEmployee.current_holders", "employeePosMaster", "employeePosMaster.orgRevisionId = :currentRevisionIdPerm");
+        // Only join if not already joined for registry systems
+        if (!posMasterAlreadyJoined) {
+          queryBuilder.innerJoin("Profile.current_holders", "posMaster", "posMaster.orgRevisionId = :currentRevisionIdPerm");
+          queryBuilder.setParameter("currentRevisionIdPerm", this.currentRevisionId);
+        }
+      } else if (tbMain === "ProfileEmployee") {
+        // Check if already joined for registry_emp systems
+        const alreadyJoined = (system === "registry_emp" || system === "registry_temp");
+        // Use the correct relation based on posMasterAlias
+        if (posMasterAlias === "employeeTempPosMaster" && !alreadyJoined) {
+          queryBuilder.innerJoin("ProfileEmployee.current_holderTemps", "employeeTempPosMaster", "employeeTempPosMaster.orgRevisionId = :currentRevisionIdPerm");
+          queryBuilder.setParameter("currentRevisionIdPerm", this.currentRevisionId);
+        } else if (posMasterAlias === "employeePosMaster" && !alreadyJoined) {
+          queryBuilder.innerJoin("ProfileEmployee.current_holders", "employeePosMaster", "employeePosMaster.orgRevisionId = :currentRevisionIdPerm");
+          queryBuilder.setParameter("currentRevisionIdPerm", this.currentRevisionId);
         }
-        queryBuilder.setParameter("currentRevisionIdPerm", this.currentRevisionId);
       }
     }