The multiple validation rules should be set in 'data-options' attribute. Please look at this code below.
<input class="easyui-validatebox" data-options="
required:true,
validType:['email','length[0,20]']
">
<input class="easyui-validatebox" data-options="
required:true,
validType:{
length:[10,30],
remote:['http://.../action.do','paramName']
}
">