diff --git a/Services/CandidateService.cs b/Services/CandidateService.cs
index dd90ae6..fc1ba9f 100644
--- a/Services/CandidateService.cs
+++ b/Services/CandidateService.cs
@@ -2025,6 +2025,21 @@ namespace BMA.EHR.Recurit.Exam.Service.Services
 
             if (status == "checkRegister")
             {
+                // เช็คเลขบัตรซ้ำ
+                var candidate2 = await _context.Candidates.AsQueryable()
+                                .Where(x =>
+                                    x.PeriodExam == exam
+                                    && x.UserId != UserId
+                                    && x.CitizenId == candidate.CitizenId
+                                    && (
+                                        (exam.Fee > 0 && x.Status.Trim().ToUpper() != "REGISTER")
+                                        || (exam.Fee == 0 && x.Status.Trim().ToUpper() == "CHECKSEAT")
+                                    )
+                                 )
+                                .FirstOrDefaultAsync();
+                if (candidate2 != null)
+                    throw new Exception(GlobalMessages.CitizanDupicate);
+
                 var subject = "แจ้งผลการสมัครสอบคัดเลือก " + exam.Name;
                 var body = candidate.FirstName + " " + candidate.LastName + " สถานะการสมัครสอบ: ได้รับใบสมัครแล้ว";
                 if (candidate.Email != null && candidate.Email != "") _mailService.SendMailToUser(subject, body, candidate.Email);