diff --git a/Frontend-Learner/components/discovery/CourseDetailView.vue b/Frontend-Learner/components/discovery/CourseDetailView.vue
index 8e741b69..380ee4c5 100644
--- a/Frontend-Learner/components/discovery/CourseDetailView.vue
+++ b/Frontend-Learner/components/discovery/CourseDetailView.vue
@@ -66,25 +66,31 @@ const handleEnroll = () => {
                          <video 
                              controls 
                              class="w-full h-full object-cover" 
-                             :poster="course.cover_image || 'https://placehold.co/800x450?text=Course+Preview'"
+                             :poster="course.thumbnail_url || course.cover_image || 'https://placehold.co/800x450?text=Course+Preview'"
                          >
                              <source :src="course.media.video_url" type="video/mp4">
                              Your browser does not support the video tag.
                          </video>
                      </template>
-                     <!-- Placeholder if no video -->
+                     <!-- Beautiful Image Showcase if no video -->
                      <template v-else>
-                         <div class="w-full h-full bg-gradient-to-br from-slate-200 to-slate-300 dark:from-slate-800 dark:to-slate-900 flex items-center justify-center relative overflow-hidden">
-                             <!-- Subtle background pattern or logo could go here -->
-                             <div class="absolute inset-0 opacity-10 dark:opacity-20">
-                                 <div class="absolute top-0 left-0 w-full h-full" style="background-image: radial-gradient(circle at 2px 2px, currentColor 1px, transparent 0); background-size: 24px 24px;"></div>
-                             </div>
+                         <div class="w-full h-full flex items-center justify-center relative overflow-hidden bg-slate-950">
+                             <!-- Show Thumbnail as Background if exists (Blurred background fill) -->
+                             <img 
+                                v-if="course.thumbnail_url || course.cover_image"
+                                :src="course.thumbnail_url || course.cover_image"
+                                class="absolute inset-0 w-full h-full object-cover opacity-30 blur-xl scale-110"
+                             />
                              
-                             <div class="relative z-10 flex flex-col items-center gap-4">
-                                <div class="w-20 h-20 bg-white/30 dark:bg-white/10 backdrop-blur-md rounded-full flex items-center justify-center ring-1 ring-white/50 shadow-xl transition-transform group-hover:scale-110 duration-500">
-                                     <q-icon name="play_arrow" size="48px" class="text-white drop-shadow-md" />
-                                </div>
-                                <span class="text-slate-500 dark:text-slate-400 font-bold tracking-wider uppercase text-xs">{{ $t('course.noVideoPreview') || 'Preview Not Available' }}</span>
+                             <!-- Main Sharp Image -->
+                             <img 
+                                v-if="course.thumbnail_url || course.cover_image"
+                                :src="course.thumbnail_url || course.cover_image"
+                                class="relative z-10 w-full h-full object-contain shadow-2xl shadow-black/50"
+                             />
+
+                             <div v-else class="absolute inset-0 bg-gradient-to-br from-slate-800 to-slate-900 flex items-center justify-center">
+                                 <q-icon name="image" size="80px" class="text-slate-700 opacity-50" />
                              </div>
                          </div>
                      </template>
diff --git a/Frontend-Learner/composables/useCourse.ts b/Frontend-Learner/composables/useCourse.ts
index ce2cd3f4..1a587eb6 100644
--- a/Frontend-Learner/composables/useCourse.ts
+++ b/Frontend-Learner/composables/useCourse.ts
@@ -18,6 +18,7 @@ export interface Course {
   approved_at?: string
   approved_by?: number
   rejection_reason?: string
+  enrolled?: boolean
   
 
   rating?: string
@@ -253,21 +254,20 @@ export const useCourse = () => {
                 message: data.message
             }
         } catch (err: any) {
-            console.error('Enroll course failed:', err)
-            
-            // เช็ค Error 409 Conflict หรือ 400 Bad Request (กรณีลงทะเบียนไปแล้ว)
-            // API ใหม่ส่ง 400 พร้อม error.code = "VALIDATION_ERROR" และ message "Already enrolled..."
             const status = err.statusCode || err.status || err.response?.status
             const errorData = err.data?.error || err.data
             
+            // เช็ค Error 409 Conflict หรือ 400 Bad Request (กรณีลงทะเบียนไปแล้ว)
+            // สำหรับกรณีนี้ เราจะไม่ log console.error ให้รกหน้าจอเพราะเป็นเรื่องที่ดักจับได้
             if (status === 409 || (status === 400 && errorData?.message?.includes('Already enrolled'))) {
                 return {
                     success: false,
                     error: 'ท่านได้ลงทะเบียนไปแล้ว',
-                    code: 409 // Treat as conflict logic internally
+                    code: 409 // treat internally as conflict
                 }
             }
 
+            console.error('Enroll course failed:', err)
             return {
                 success: false,
                 error: errorData?.message || err.message || 'Error enrolling in course',
diff --git a/Frontend-Learner/nuxt.config.ts b/Frontend-Learner/nuxt.config.ts
index 0ab78514..b3079964 100644
--- a/Frontend-Learner/nuxt.config.ts
+++ b/Frontend-Learner/nuxt.config.ts
@@ -36,7 +36,7 @@ export default defineNuxtConfig({
     extras: {
       fontIcons: ["material-icons"],
     },
-    plugins: ["Notify"], // เปิดใช้ Plugin Notify
+    plugins: ["Notify", "Dialog"], // เปิดใช้ Plugin Notify และ Dialog
     config: {
       brand: { // กำหนดชุดสีหลัก (Theme Colors)
         primary: "#4b82f7",
diff --git a/Frontend-Learner/pages/course/[id].vue b/Frontend-Learner/pages/course/[id].vue
index aef56e85..9c559339 100644
--- a/Frontend-Learner/pages/course/[id].vue
+++ b/Frontend-Learner/pages/course/[id].vue
@@ -31,6 +31,23 @@ const isEnrolling = ref(false)
 const handleEnroll = async () => {
     if (!course.value) return
     if (isEnrolling.value) return
+
+    // กรณีเคยกดลงทะเบียนไปแล้ว (Check จากสถานะคอร์ส)
+        if (course.value.enrolled) {
+        $q.dialog({
+            message: `<div class="text-slate-800 text-base leading-relaxed">ท่านเคยลงทะเบียนคอร์ส <b class="text-blue-600">"${getLocalizedText(course.value.title)}"</b> นี้ไปเรียบร้อยแล้ว</div>`,
+            html: true,
+            ok: {
+                label: 'ตกลง',
+                color: 'primary',
+                rounded: true,
+                unelevated: true,
+                padding: '8px 32px'
+            }
+        })
+        return
+    }
+
     isEnrolling.value = true
 
     // เรียก API ลงทะเบียนเรียน
@@ -38,7 +55,6 @@ const handleEnroll = async () => {
 
     if (res.success) {
         // ถ้าสำเร็จ ให้เปลี่ยนหน้าไปที่ "คอร์สของฉัน" พร้อม params enrolled=true
-        // Use object syntax for robust query param handling
         const targetId = route.params.id || course.value?.id
         return navigateTo({
             path: '/dashboard/my-courses',
@@ -47,14 +63,30 @@ const handleEnroll = async () => {
                 course_id: String(targetId)
             }
         })
-        // กรณี error แสดง Toast notification แทน alert
-        $q.notify({
-            type: 'negative',
-            message: res.error || 'Failed to enroll',
-            position: 'top',
-            timeout: 3000,
-            actions: [{ icon: 'close', color: 'white' }]
-        })
+    } else {
+        // กรณี API แจ้งว่าเคยลงทะเบียนไปแล้ว (Code 409)
+        if (res.code === 409) {
+            $q.dialog({
+                message: `<div class="text-slate-800 text-base leading-relaxed">ท่านเคยลงทะเบียนคอร์ส <b class="text-blue-600">"${getLocalizedText(course.value.title)}"</b> นี้ไปเรียบร้อยแล้ว</div>`,
+                html: true,
+                ok: {
+                    label: 'ตกลง',
+                    color: 'primary',
+                    rounded: true,
+                    unelevated: true,
+                    padding: '8px 32px'
+                }
+            })
+        } else {
+            // กรณี error ทั่วไป แสดง Toast notification
+            $q.notify({
+                type: 'negative',
+                message: res.error || 'Failed to enroll',
+                position: 'top',
+                timeout: 3000,
+                actions: [{ icon: 'close', color: 'white' }]
+            })
+        }
     }
 
     isEnrolling.value = false