TinyMCE load in jQuery Post

I want to load TinyMCE ( https://www.tinymce.com/download/ ) to a textarea field within my Jquery post code below...

HTML

<script src="//cdn.tinymce.com/4/tinymce.min.js"></script>
<script>

tinyMCE.init({
        mode : "textareas",
        theme : "advanced"
});

</script>

<div id="Column1" class="ListResults"></div>

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Query code...

		$.post( "bespoke_page_script.php", {
									cust_id: $('#customer_id').find(":selected").val()
        						}, function(data) { 
			
		$( ".ListResults" ).html( data );
		tinymce.EditorManager.execCommand('mceAddEditor', false, "message_to_customer");	
							
		});

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Code in bespoke_page_script.php ...

<p>
<label for="message_to_customer">Message to Customer</label>
<textarea name="message_to_customer" id="message_to_customer" cols="45" rows="10">
Dear xxxx
</textarea>
</p>

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It's not work for me. What am I doing wrong. Can you please send me revised working code please.