Indian Railways operates a train from Thoothukudi to Kochi once daily. Tickets cost $8 - $19 and the journey takes 8 h 25 min. Alternatively, you can take a bus from Thoothukudi to Kochi via Coimbatore and Ernakulam in around 12 h 55 min.
From Tuti Melur (TME) train to Maniyachchi Junction (MEJ) then train to Eranakulam Junction (ERS). 9 h 53 min ₹1,750. From Thoothukudi bus to Coimbatore, bus to Ernakulam, then taxi to Kochi. 12 h 55 min ₹1,508. From Thoothukudi taxi to Kochi. 4 h 48 min ₹5,512. From Thoothukudi drive to Kochi. 4 h 48 min ₹2,556. From Thoothukudi taxi to Tuticorin airport, fly to Kochi airport, then taxi to Kochi. 6 h 41 min ₹8,775.