diff --git a/backend/src/modules/ai/services/ocr.service.ts b/backend/src/modules/ai/services/ocr.service.ts
index 8b3324c3..467dd26c 100644
--- a/backend/src/modules/ai/services/ocr.service.ts
+++ b/backend/src/modules/ai/services/ocr.service.ts
@@ -2,6 +2,7 @@
 // Change Log
 // - 2026-05-15: เพิ่ม OCR auto-detection service สำหรับ ADR-023A.
 // - 2026-05-25: แก้ไข AggregateError (empty message) จาก axios โดย wrap เป็น Error พร้อม context ที่ชัดเจน.
+// - 2026-05-25: เพิ่ม path remapping (OCR_UPLOAD_BASE_PATH) เพื่อแปลง local upload path เป็น path ที่ sidecar เห็นผ่าน CIFS.
 
 import { Injectable, Logger } from '@nestjs/common';
 import { ConfigService } from '@nestjs/config';
@@ -28,6 +29,8 @@ export class OcrService {
   private readonly logger = new Logger(OcrService.name);
   private readonly threshold: number;
   private readonly ocrApiUrl: string;
+  private readonly localUploadBase: string;
+  private readonly sidecarUploadBase: string;
 
   constructor(private readonly configService: ConfigService) {
     this.threshold = this.configService.get<number>('OCR_CHAR_THRESHOLD', 100);
@@ -35,6 +38,22 @@ export class OcrService {
       'OCR_API_URL',
       'http://localhost:8765'
     );
+    // path ที่ backend เห็น → path ที่ sidecar เห็น (ผ่าน CIFS mount)
+    this.localUploadBase = this.configService
+      .get<string>('UPLOAD_PERMANENT_DIR', '/app/uploads/permanent')
+      .replace(/\/permanent$/, '');
+    this.sidecarUploadBase = this.configService.get<string>(
+      'OCR_SIDECAR_UPLOAD_BASE',
+      '/mnt/uploads'
+    );
+  }
+
+  /** แปลง local upload path เป็น path ที่ sidecar เห็นผ่าน CIFS mount */
+  private remapPath(localPath: string): string {
+    if (this.localUploadBase && localPath.startsWith(this.localUploadBase)) {
+      return localPath.replace(this.localUploadBase, this.sidecarUploadBase);
+    }
+    return localPath;
   }
 
   /** ตรวจสอบ text layer ก่อนเลือก OCR slow path */
@@ -54,9 +73,11 @@ export class OcrService {
     }
 
     try {
+      const sidecarPath = this.remapPath(input.pdfPath);
+      this.logger.debug(`OCR path remap: ${input.pdfPath} → ${sidecarPath}`);
       const response = await axios.post<PaddleOcrResponse>(
         `${this.ocrApiUrl}/ocr`,
-        { pdfPath: input.pdfPath },
+        { pdfPath: sidecarPath },
         { timeout: 90000 }
       );
       return {
diff --git a/specs/04-Infrastructure-OPS/04-00-docker-compose/QNAP/app/.env.example b/specs/04-Infrastructure-OPS/04-00-docker-compose/QNAP/app/.env.example
index 0a220482..901aa148 100644
--- a/specs/04-Infrastructure-OPS/04-00-docker-compose/QNAP/app/.env.example
+++ b/specs/04-Infrastructure-OPS/04-00-docker-compose/QNAP/app/.env.example
@@ -88,6 +88,7 @@ OLLAMA_URL=http://192.168.10.100:11434
 # PaddleOCR Sidecar (Admin Desktop Desk-5439 — ADR-023A)
 OCR_API_URL=http://192.168.10.100:8765
 OCR_CHAR_THRESHOLD=100
+OCR_SIDECAR_UPLOAD_BASE=/mnt/uploads
 
 # Thai preprocessing microservice (PyThaiNLP — Admin Desktop)
 THAI_PREPROCESS_URL=http://192.168.10.100:8765
diff --git a/specs/04-Infrastructure-OPS/04-00-docker-compose/QNAP/app/docker-compose-app.yml b/specs/04-Infrastructure-OPS/04-00-docker-compose/QNAP/app/docker-compose-app.yml
index b26f6552..3c200850 100644
--- a/specs/04-Infrastructure-OPS/04-00-docker-compose/QNAP/app/docker-compose-app.yml
+++ b/specs/04-Infrastructure-OPS/04-00-docker-compose/QNAP/app/docker-compose-app.yml
@@ -98,6 +98,7 @@ services:
       # --- PaddleOCR Sidecar (Desk-5439 — ADR-023A) ---
       OCR_API_URL: ${OCR_API_URL:?OCR_API_URL required}
       OCR_CHAR_THRESHOLD: ${OCR_CHAR_THRESHOLD:-100}
+      OCR_SIDECAR_UPLOAD_BASE: ${OCR_SIDECAR_UPLOAD_BASE:-/mnt/uploads}
       # --- Numbering ---
       NUMBERING_LOCK_TIMEOUT: '5000'
       NUMBERING_RESERVATION_TTL: '300'