He might be a tiny bit on the thin side, but very little. He's just a smaller snake. His body seems well proportioned, so I doubt there is really a problem.
You mention he seems hungry all the time, can you elaborate on that ? Do you just see him out and about, or is he actively tracking movement and heat around his tub all the time ?
If he is actively tracking heat signatures, then he is actually hungry and you need to look into that. Once you get your scale, weigh him and then weigh his food. Ideally you want his food to be 10 - 15% of his weight. So if he weighs 500 grams, you want his food to be 50 grams or so. This rule changes once he hits about 1000 grams, I never feed a meal bigger than 100 grams except for the biggest of my females.
If he's eating the right size of food and he's eating every 5 days, I would consider a fecal check just to be sure.
Gale