If my geography is correct, I think the following rule prohibits what you are trying to do.
<font face="Verdana, Arial, Helvetica" size="2">TRAVEL MUST INCLUDE ONLY ONE TRANS-ATLANTIC CROSSING AND ONLY ONE TRANS-PACIFIC CROSSING. NOT MORE THAN ONE TRANS-SIBERIAN CROSSING MAY BE PERMITTED IN AN ENTIRE JOURNEY.</font>
I don't think you can go FRA-PEK-VIE-SIN without crossing Siberia three times.
Of course, if LH will ticket it...