The State Railway of Thailand (SRT) has announced plans to extend the red line of the Bangkok mass-transit system. The 53.84 km of the extension will be carried out on the public-private partnership (PPP) model. With an estimated total  cost of TBH67.5 billion (US$2.02 billion), the project will be divided into the following four sections:

1. Rangsit-Thammasat University Rangsit- 8.84 km line with an investment of  TBH6.57 billion (US$197 million);
2. Taling Chan-Salaya- 14.8 km line with an investment of TBH10.2 billion (US$306 million);
3. Taling Chan-Siriraj: 4.3 km line with an investment of TBH6.64 billion (US$199 million);
4. Bang Sue-Hua Lamphong and Bang Sue-Hua Mark- 25.9 km line with an investment of TBH44.1 billion (US$1.32 billion).

The bidding process is scheduled to start in January 2022, and the project is expected to be operational in 2025.