PHP JQuery สร้างฟอร์มเพิ่มข้อมูลแล้วแต่บันทึกข้อมูลภาษาไทยไม่ได้ครับ

<link href="js/jquery-ui.min.css" rel="stylesheet">
<script src="js/jquery-2.1.1.min.js"> </script>
<script src="js/jquery-ui.min.js"> </script>
<script src="js/jquery.form.min.js"></script>
<script src="js/jquery.blockUI.js"></script>
<script>

$(function() {
	$('a.write-comment').click(function(event) {   //เมื่อคลิกลิงค์ "แสดงความคิดเห็น"
		$('#form-comment')[0].reset();

		event.preventDefault();
		
		var t = "แสดงความคิดเห็น";

		$('#form-dialog').dialog({
			width: '600px',
			title: t,
			modal: true,
			position: { my: "center", at: "center", of: window}  	//เป็นค่า default อยู่แล้ว
		});
		
		//กำหนดค่าให้แก่อิลิเมนต์ชนิด hidden ทั้งสองอัน
		$('#question-id').val($(this).attr('data-id'));
		
	});

		
	$('#submit-comment').click(function() { 
	
		$('form#form-comment').ajaxForm({
			url: 'webboard_save-comment.php',
			type: 'post',
			dataType: 'script',
			beforeSend: function() {
				$.blockUI({message:'<h3>กำลังส่งข้อมูล...</h3>'});
			}, 
			complete: function() {
	
				$.unblockUI();
		
			}
		});	
	});
});
</script>

  <article>
 <?php

	$question_id = (int)$_GET['id'];
	
	echo $_GET['id'];
		
	$sql = "SELECT * FROM tbl_webboard_question WHERE id = $question_id";
	$r = dbQuery($sql);
	while($a = dbFetchArray($r)) {
		
		$topic = $a['topic'];
		$user_id = $a['user_id'];
		$date_post = thai_date($a['date_post']);
		$detail = $a['detail'];
		$views = $a['views'] + 1;
	
	
		echo '<div class="topic">'. $topic . '</div>';
		echo '<div class="above">ผู้เขียน: '. $a['user_id'] . '<span>' . $date_post . '</span></div>';
		echo '<div class="article">'. $detail . '</div>';
	
		echo '<div class="below">';
		
			echo '<a href="#" class="write-comment" data-id="'.$question_id.'">แสดงความคิดเห็น</a>';
			echo " | ";
			
			echo $question_id;
			echo "<a href='webboard_edit-question.php?id=" . $question_id . "' >แก้ไข</a>";
			
			echo " | ";
			
			echo "<a href='webboard_del-question.php?id=" . $question_id . "'>ลบ</a>";		
			
	
			$sql = "SELECT COUNT(*) FROM tbl_webboard_answer WHERE question_id = $question_id ";
			$r = dbQuery($sql);
			$row = dbFetchRow($r);
			$num_comments = $row[0];
		
		if($num_comments!= 0 ){
			echo "<span>ความคิดเห็น($num_comments)&nbsp;&middot;&nbsp;";
	
		echo '</div>';
	
		$sql_u = "UPDATE tbl_webboard_question SET views = views + 1 WHERE id = $question_id;";
	 	dbQuery($sql_u);
		}
		
	}
?>
<br/>

<div id="form-dialog">

<form id="form-comment" method="post">


    <textarea name="detail" placeholder="ความคิดเห็น *"></textarea><br/>
    
    <button type="submit" id="submit-comment">ส่งข้อมูล</button>
    
    <input type="hidden" name="user_id" value="<?php echo $user_id ?>" readonly > 
    <input type="hidden" name="question_id" id="question-id">
    
</form>
</div>

<?php
require_once '../library/config.php';


	if($_POST['detail'] == "") {
		echo "alert('ใส่ข้อมูลยังไม่ครบ');";
		exit;
	}

	$id = $_POST['question_id'];
	$user_id = $_POST['user_id'];
	$text = $_POST['detail'];

	$sql = "INSERT INTO tbl_webboard_answer VALUES('', '$id', '$text', '$user_id', NOW())";


	if(dbQuery($sql)) {
		
		echo "\$('#form-dialog').dialog('close'); 
				location.reload();";
	}
	else {
		echo "alert('เกิดข้อผิดพลาดในการบันทึกข้อมูล กรุณาลองใหม่')";
	}
	
?>