What is a "triple interlocking stitch"?
That was made by a triple needle chain stitch machine.  You can tell it was done in one pass with a triple needle machine because the holes align perfectly along the length of the stitch (making it very likely they were all formed at the same time).

You can tell it's a chain stitch (as opposed to a lock stitch, which a typical household sewing machine makes) by the way the stitches are formed on the back.  Another common place to see chain stitches in your house is on jeans.

The main advantage of chain stitching (and the reason it is used in commercial applications like this) is that it doesn't require a bobbin.  A home sewing machine is a lock stitch machine, which means the top thread is twisted around a bottom thread by passing over the bobbin on each stitch.  The bobbin is limited in size because the top thread has to go around it.  A chain stitch machine can sew much longer without interruption.

In particular, I think I see three threads on the back, which is a double chain stitch.  Those extra threads don't actually add any strength.  More the opposite -- chain stitches can easily be unraveled if the thread breaks, just like pulling apart a row of knitting.

If you want to recreate that seam, just sew three times with your home machine on straight stitch.  You won't be able to recreate the stitch length (your home machine just won't make stitches that long), which will cause a bit of extra puckering (shortening along the seam).

By far more important than exactly what stitch you use is to use a good bonded polyester thread or an outdoor item like a hammock will fall apart when the thread rots.

(If you want to see an industrial machine that could do this, Google something like "triple needle six thread chain stitch".  Six threads because it's a double chain stitch.)