[2] In August 2021, Sreenidi Deccan roped in Lalchungnunga, on a two-year deal with an option to extend by another year.
[7][8] Lalchungnunga made his league debut for East Bengal on 7 October against Kerala Blasters in a 1–3 defeat.
[9] On 25 December 2022, East Bengal announced that Lalchungnunga has signed permanently for the club, effective from 1 June 2023, until 2026.
[10] In the 2023–24 season, Lalchungnunga led the East Bengal defence to the Durand Cup final where they finished runners-up, and was part of the 2024 Indian Super Cup winning team as he came on as a substitute in the final against Odisha as East Bengal became champions at the Kalinga Stadium.
On 21 November 2023, Lalchungnunga made his senior international debut when he came on as a substitution for Sandesh Jhingan in the 91st minute against Qatar in the 2026 FIFA World Cup qualification – AFC second round match at the Kalinga Stadium in Bhubaneshwar.