I just changed buddy passes from the home computer for 2 overseas travelers.
This has to be done by the employee or at a Delta ticket office or as re-issue on the phone.
I changed my buddy tkts departure airport from Budapest to Prague to return to the States. There was a refund of a few bucks which came off their credit card (which was used to buy the pass travel)
Just make a decision and contact your employee--best not to create too much difficulty (Did they use your credit car OR Are they ok if it costs more and you can reimburse them? You won't have any Malaysia routes--closest thing is Vietnam? Not sure if service has started? There are embargoes on some buddy pass travel this time of year.
I recommend you check the Delta.com website, make tentative plans and ask your employee if they would mind doing the change for you.