Kannan(Sarathkumar) and Das(Napolean) have been the closest of friends since childhood and think of Uma(Aswati) as their common sister. Coming to Thenkaasi as orphans and paupers, they have since grown to control the local market, in the process earning the ire of the previous owner Devaraj(P.Vasu). Meenakshi(Samyukta Varma), Devaraj's daughter, is in love with Kannan and after considerable wooing, makes him reciprocate her affections. Sangeetha(Devayani), a singer, takes refuge in the duo's house when they become the cause for her being driven out of her house. Circumstances then result in Das mistaking Meenakshi to be in love with him while Sangeetha thinks that Kannan is in love with her.

Thenkaasi Pattanam falls into a rather unique category among recent movies. It is not a full-length comedy like Panchatantiram or Charlie Chaplin , with logic thrown to the winds for the sake of laughs. It is pretty strong on sentiments like friendship and love and though the happenings require suspension of disbelief on our parts, they are not completely illogical or chaotic. On the other hand, the movie does tackle most of the scenes in a humorous vein and maintains a tone that suggests that it is never to be taken seriously. It blends its comedy into the story without the need for a separate comedy track and as a result, contains segments that rival the aforementioned comedies in terms of the laughs generated.

While the serious portions of the movie manage to be quite entertaining with interesting knots and a little suspense on how they are going to be unravelled, the strength of the movie lies in its comedy. The characters of both Sarathkumar and Napolean have been developed with lightheartedness with their short tempers, brash attitudes and loud clothes. But it is Vivek who steals the show from under their noses. As their sister's suitor, he has an important role and his lines are very funny. The sequence where he and Charlie dress up as a cow easily ranks as one of the funniest sequences in recent times. Their idea when Kumarimuthu arrives to milk the cow is crude but hilariously clever and the acts of the cow lead to unbridled laughter.

The main storyline itself contains enough twists and turns to keep us hooked. The circumstances needed to make Napolean and Devayani confused about their future spouses are handled well without seeming implausible or idiotic. And once the pieces are in place, the movie is successful in maintaining the little suspense about when the truths will come out and how it will affect the relationships. Things do drag in the middle though with needless scenes arising out of Napolean's assumption that he is going to wed Samyuktha Varma. Delhi Ganesh and 'Kovai' Sarala as Devayani's relatives, add nothing to the proceedings. The climax manages to resolve things quite satisfactorily.

It is a relief that Sarathkumar and Napolean, political allies in real-life, manage to keep politics and rabble-rousing talk out. Samyuktha Varma looks pretty and has very expressive eyes that she uses to good effect. Deyavayani suffers from a poorly defined character and remains in the sidelines most of the time. Vivek is at his funniest and Charlie, for a change, provides him good support. P.Vasu is an inconsequential villain with mostly empty threats. Suresh Peters' tunes dont stay with us once they are done but the song sequences too have been picturised in a comic manner. The duet between Sarathkumar and Samyuktha Varma, with Vivek in the middle, is a case in point.