User blog comment:Omega natsu2/Chapter 369: The Place Prayers Reach, Predictions./@comment-31.132.65.50-20140129025714/@comment-24467372-20140129170932

It can have a physical form if you put enough magic into it. Laxus's was a hologram whereas Siegrain touched Erza and almost kissed her.

In fact I believe the Thought Projection that touched Erza wasn't even Siegrain. Siegrain was at Era and Jellal was at ToH. So,even the TP that a TP created has a physical form.