The Bangkok Metropolitan Administration (BMA) is looking for private companies to invest in its Grey Line monorail PPP Project in Bangkok, Thailand. BMA has already conducted a "Market Sounding" public discussion seeking interested companies to voice their opinions on the monorail project.

The 40 km long Grey Line is expected to serve the needs of about 140,000 commuters daily and will link Watcharapol and Tha Phra via the Rama IX Bridge in the southern part of downtown Bangkok. The new line will connect with other commuter lines including the MRT Pink Line, MRT Yellow Line, MRT Orange Line, SRT Light Red Line and BTS Skytrain Sukhumvit Line.

The project has an estimated investment of THB27.8 billion (US$830.58 million). The construction works for the project are planned to start in 2026, and services will commence by 2030.