One day, while riding his bike, Ashwin's comes in collision with a car. After the accident, Arjay steps out of the car and verbally abuses Ashwin, who ends up thrashing him in return. However, he later apologizes and the two then leave the spot.
Later, Ashwin, who after completing his final year and heads to collect his degree certificate is in for a shock when it is mentioned that he has a black mark in terms of conduct. When he inquires the management how such a thing could have been stated, he comes to realize Arjay is the son of the owner of the college, A. L. Azhagappan. He then comprehends that Arjay has done this solely to take revenge on him. Ashwin decides to take matters into his own hands and attempts to get his conduct certificate rectified without letting know his father. He goes to meet Azhagappan, who is primarily known to be a key figure in politics and is preparing ahead for the upcoming elections. When Ashwin comes to meet him, Azhagappan thrashes him up using his henchmen. The rest of the plot from this point on revolves around Ashwin seeking his revenge against Arjay, his efforts to get his conduct certificate rectified and also destroying Azhagappan's political ambitions.
Ashwin has owned the role given to him and has come out on top in all departments - be it action, romance, sentiment, he has delivered a commendable performance. Swathi, as her previous appearances once again charms and delights us with her cuteness and, takes it up a notch higher portraying a bold and fearless character this time. Although Arjay appears only in few scenes compared to the film's leads, he has left a solid impression as the prime antagonist. Jayaprakash has brought in all his experience and has delivered a satisfactory performance yet again. A. L. Azhagappan terrorizes the screen with his majestic appearance and breathes life into the role of a rowdy as well as a politician. Karunakaran, Daniel Anne Pope, Sendrayan and Anupama Kumar have portrayed their supporting roles in a neat manner.
First up, director S. Ashok Amritaraj needs to be complimented for his attempt to tell a story primarily centered around the relationship between a father and a son. He has thrown light on how a youngster from a middle-class background goes through hardships he encounters in his daily life. In addition, he has also given noteworthy suggestions on why education is a must and why it needs to be free of cost for everyone. Despite his tremendous efforts, the filmmaker could have paid more attention towards the screenplay as the transition in certain scenes to the next seems off-putting. Ajesh Ashok's songs are good to listen and has shone in the background score department too. GK Venkatesh's cinematography skills come to the fore and he has the shot film well.
In short, Thiri could have lit better.