I was a backpack virgin and have now been in SE Asia for Three months. I love it and am so glad i came here as i've seen such incredible sights and met some completely amazing people. I would strongly recommend visiting Laos, cambodia and Vietnam. Six months gives you more than enought time to visit everything you want to see and the other countries too, and i would recommend everyone goes to laos, i simply loved it.
Have an amazing trip - and good luck!