If you know how to double tongue, then it should be easy to triple.
Here is our Melody:
There are two ways of triple tonguing this. The first way is easier but not as effective. On each triplet say: Do-Gu-Do. This is slow at first but you can work it up to a good tempo. The problem with this way is that eventually you will not be able to get it any faster.
The second, and better way, of triple tonguing is this:
This way you never break the pattern any you can work it up to a much faster speed.