Thomas controlled him most of the game but that's pretty standard when talking about a top 10-12 pick LT who may very well be the first OL off the board. Of course on the other side is Isaiah Wilson who is seemingly going to be a top 50 pick and possibly even a late 1st.
At the end of the day Chaisson beat Wilson clean for a sack with an inside spin (Q3/5:56) and beat Thomas for what was a sack for all intents and purposes (Q3/:11). Chaisson got the jump on Thomas with his burst several times but Thomas usually recovered to get back to even with his length, on this particular play Thomas couldn't recover and Chaisson showed great bend to close on the QB. In the boxscore it's an incomplete pass but the eye test tells you that it was 1/10th of a second from a sack or even strip sack, and I'm not totally convinced his hand was moving forward before the ball was out.
Chaisson is raw as far as his pass rush plan/stringing together counter moves so it's not a surprise that Thomas often was able to recover using his length against Chaisson's initial burst, but ultimately Chaisson put up a sack and missed another by a split second against possibly two first round OT's.
What I personally love about his game is that he's very fundamentally sound against the run for his size/age/experience level and doesn't back down against guys outweighing him by 60+ lbs. There are several times where he goes 1-on-1 against either Thomas or Wilson and sets the edge without giving any ground, resulting in runs for little to no gain.
Combine that with the pass rush upside and natural explosiveness that he brings off the edge and that's why I'm taking him 100 times out of 100 over pretty much anybody that's likely to be available at 17. Kinlaw is the one guy I'd take over him, assuming the top WR's are gone.
Other impressive plays in case you're interested:
Q1: 7:54 (sets the edge 1-on-1 vs. Thomas, stacks/sheds and strings the run out to the sideline, goes for no gain), 2:48 (reads screen immediately, doesn't unnecessarily engage Thomas, explodes directly into backfield and knocks down pass)
Q2: 8:40 (sets edge 1-on-1 vs. Wilson, doesn't provide escape route to RB with middle clogged who is forced to dive head first into pile for no gain), 1:46 (gets jump on Thomas with his burst but as he usually does Thomas recovers to stop him from a free run at the QB, Chaisson does gets near the QB and starts working back inside but the ball is out in 2 seconds, it's hard to say Chaisson directly forced the poor decision but it was a rushed decision and a relatively poor one to throw a jump ball towards Stingley who was in better position than the WR when the ball was released, and it was made with Chaisson bearing down and the only LSU rusher near the QB, end result is an INT)
Q3: 7:07 (beats Wilson with a quick inside club, forces early/errant throw), 6:58 (sets the edge again 1-on-1 vs. Thomas on zone RPO action, doesn't get pushed off the LOS even an inch, stacks and holds for several seconds before shedding and again stringing run out to the sideline for little gain)