The State Railway of Thailand signed 5 contracts on Thursday (26 Nov 2020) including a tunnel construction between Muak Lek-Lam Takhong. In the news the distance is 12.23km (I don't know if it is all tunnel length).

Thai company Navarat Pattanakarn Plc won it. The contract is worth 4.2 billion baht.

Tunnel is part of Thai-Chinese high-speed railway project between Bangkok and Nakhon Ratchasima.

https://www.bangkokpost.com/business/2025979/b40bn-high-speed-train-contracts-inked