First of all, he's really cute!
He does look skinnier in the other photo compared to the first.
However, 82 grams isn't too low for a tiel, as they tend to be 80-120grams,
but if your tiel is losing weight, (or), show any sign of sickness you should get him checked out by an avian vet.
Is he eating normally?
Does he show sign of sickness?
Monitor your bird carefully just in case : )
Hope this helps!
All the best,