I have a form with multiple TinyMCE editors. Some of the editors are advance and some are simple editors. I have used jquery validation plugin for validation in client-side.
$('#submit').click(function() {
for (i=0; i < tinymce.editors.length; i++){
var content = tinymce.editors[i].getContent(); // get the content
$('#description').val(content); // put it in the textarea
}
});