THHN to NM-B wiring, Transition from External Piping Conduit to in wall junction box
The problem with a project like this is that the code doesn't really want you to get creative with line voltage power.  That's for good reasons:  there are a lot of potential hazards if you go afoul of the code.  

The unprotected splice from THHN stranded to NM in the wall is a no-go.  You might be able to work something out with a box and cover that work with the pipe floor flange but you probably won't like the way it looks.  

If the piping is seen as a home made non-listed light fixture, that's frowned upon.  If you look at the piping as a protective sleeve for NM cable - and run NM with jacket in the piping - it might fly, but it would still be in a gray area at best.  Then again considering the piping as part of the home's structure - that might fly, but you'll still probably need a box at the fixture.  

If an inspector doesn't see it the way you do, you have a headache.  

Grounding / bonding the piping is a real issue and screwing that up could create some pretty scary hazards.  

There is a simple alternative.  If you're going to get creative, get creative with low voltage lighting, the hazards are drastically reduced, and the code requirements reflect this.  It goes from fuzzy gray area pain in the butt hurt somebody / start a fire worries, to do just about whatever you want and nobody cares.