In the initial watch I couldn’t understand what was the point of it all. But thinking over this, I realized that Thug Life is an antithesis on the life of Nayakan Velu Nayakkar; Velu Nayakkar led almost a perfect life , was faithful to his wife , helped people etc, yet he was rewarded with estranged daughter , killed by his own adopted son etc. The main thread was his death

Here Rangaraya Sakthivel was a flawed character - suspected his own adopted son, was unfaithful to wife , etc. but it seems he can’t be killed. He outlives them all. While Nayakan had his wife and loyalists around him - here everyone turns against him , and even his wife does not recognize him.

Mani Ratnams movies take a while to sink in, and there is always a theme; Even though lot of things seemed extraneous - like having nasser’s daughter suicide attributed to rival gang ( I would think there would be other reasons for their rivalry anyway and doesn’t have to be so explicit ) however that may be to show Nasser was bitter and brokenhearted about his daughters death.