Please look at this example. It works fine.
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Load Form Data - jQuery EasyUI Demo</title>
<link rel="stylesheet" type="text/css" href="https://www.jeasyui.com/easyui/themes/default/easyui.css">
<link rel="stylesheet" type="text/css" href="https://www.jeasyui.com/easyui/themes/icon.css">
<script type="text/javascript" src="https://www.jeasyui.com/easyui/jquery.min.js"></script>
<script type="text/javascript" src="https://www.jeasyui.com/easyui/jquery.easyui.min.js"></script>
<script type="text/javascript">
$(function(){
$('#ff').form('load',{
gender:'male',
name:'myname',
email:'mymail@gmail.com',
subject:'subject'
});
})
</script>
</head>
<body>
<h2>Load Form Data</h2>
<div class="easyui-panel" title="New Topic" style="width:100%;max-width:500px;padding:30px 60px;">
<form id="ff" method="post">
<div style="margin-bottom:20px">
<label class="textbox-label textbox-label-before">Gender:</label>
<input class="easyui-radiobutton" name="gender" data-options="label:'female',labelPosition:'after',value:'female'">
<input class="easyui-radiobutton" name="gender" data-options="label:'male',labelPosition:'after',value:'male'">
</div>
<div style="margin-bottom:20px">
<input class="easyui-textbox" name="name" style="width:100%" data-options="label:'Name:',required:true">
</div>
<div style="margin-bottom:20px">
<input class="easyui-textbox" name="email" style="width:100%" data-options="label:'Email:',required:true,validType:'email'">
</div>
<div style="margin-bottom:20px">
<input class="easyui-textbox" name="subject" style="width:100%" data-options="label:'Subject:',required:true">
</div>
</form>
</div>
</body>
</html>