Public Function GenMonthThai(ByVal intMonth As Integer, ByVal intParameter As Integer)
        Dim strMonth As String = String.Empty
        Select Case intMonth.ToString
            Case "1"
                If intParameter = 1 Then
                    strMonth = "ม.ค"
                ElseIf intParameter = 2 Then
                    strMonth = "มกราคม"
                End If

            Case "2"
                If intParameter = 1 Then
                    strMonth = "ก.พ"
                ElseIf intParameter = 2 Then
                    strMonth = "กุมภาพันธ์"
                End If

            Case "3"
                If intParameter = 1 Then
                    strMonth = "มี.ค"
                ElseIf intParameter = 2 Then
                    strMonth = "มีนาคม"
                End If

            Case "4"
                If intParameter = 1 Then
                    strMonth = "เม.ษ"
                ElseIf intParameter = 2 Then
                    strMonth = "เมษายน"
                End If

            Case "5"
                If intParameter = 1 Then
                    strMonth = "พ.ค"
                ElseIf intParameter = 2 Then
                    strMonth = "พฤษภาคม"
                End If

            Case "6"
                If intParameter = 1 Then
                    strMonth = "มิ.ย"
                ElseIf intParameter = 2 Then
                    strMonth = "มิถุนายน"
                End If

            Case "7"
                If intParameter = 1 Then
                    strMonth = "ก.ค"
                ElseIf intParameter = 2 Then
                    strMonth = "กรกฏาคม"
                End If

            Case "8"
                If intParameter = 1 Then
                    strMonth = "ส.ค"
                ElseIf intParameter = 2 Then
                    strMonth = "สิงหาคม"
                End If

            Case "9"
                If intParameter = 1 Then
                    strMonth = "ก.ย"
                ElseIf intParameter = 2 Then
                    strMonth = "กันยายน"
                End If

            Case "10"
                If intParameter = 1 Then
                    strMonth = "ต.ค"
                ElseIf intParameter = 2 Then
                    strMonth = "ตุลาคม"
                End If

            Case "11"
                If intParameter = 1 Then
                    strMonth = "พ.ย"
                ElseIf intParameter = 2 Then
                    strMonth = "พฤศจิกายน"
                End If

            Case "12"
                If intParameter = 1 Then
                    strMonth = "ธ.ค"
                ElseIf intParameter = 2 Then
                    strMonth = "ธันวาคม"
                End If

        End Select
        Return strMonth
    End Function


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ตัวอย่างคำสั่งสำหรับดึงฟังชั่นมาใช้

Dim strDate = "8/5/2555 15:59:37"

MsgBox(Day(strDate) & " - " & GenMonthThai(Month(strDate), 1) & " - " & Year(strDate) & "Time=" & String.Format(strDate, Now.Hour, Now.Minute, Now.Second))


ลองนำไปดัดแปลงดูนะครับ