If the file contains multiple languages, right-click in your player, select Audio > Audio Track , and ensure the Tamil track is selected.

If the file fails to play on certain smart TVs, you may need to "remux" it using MKVMerge to ensure the tracks are ordered correctly for your specific player. MKV Files Explained - Adobe

The MKV format is a container that can hold multiple tracks. For this specific Tamil release:

Ensure your server is set to "Direct Play" to avoid transcoding, which can be heavy on your hardware for HEVC 720p files.

If the Tamil audio doesn't match the lip movements, players like VLC allow you to fix this on the fly. Press the J or K keys to shift audio backward or forward in 50ms increments.