TinyMCE kindly converts my URLs to relative links, but eventually it breaks the content link in my case. In order to avoid that situation,
If you put the original link as following
<img src="http://myserver.com/img/howdy.jpg">
and found that URL is changed like:
<img src="../howdy.jpg">
You are in the same situation like me.
To remove above issue in TinyMCE, you should add below options in TinyMCE.init(...)
relative_urls: false, convert_urls: false, remove_script_host : false,