Thomm is the leader of the HugeMungus Rock kobold tribe in the borderlands / Duchy of ThornCryf. Go to Asyl, walk into the mist his encampment is by the lake. I think he is on the west side of the lake if memory serves.
In the past, he needs to be tired out before really being able to talk. I'd prepare for a fight.
His immense patience during Dragon's Fall was a new development and one I would not expect to see again for a while.
-Gideon