The Bangkok Metropolitan Administration (BMA) is seeking private companies interested in investing in its Grey Line monorail project as construction is due to begin in 2026.

The BMA on Thursday held a “Market Sounding” public discussion, calling on affiliated private companies to voice their opinions on the Grey Line, a planned monorail project linking the Vacharapol area in northern Bangkok with Thong Lor in the Sukhumvit business area.

During the talks, BMA officials presented engineering and environmental data, including potential investment opportunities in the public and private sectors.

Construction of the Grey Line will start in 2026, and services will commence by 2030, according to the BMA.

The number of passengers in the first operating year is expected to be about 97,000 people per day, while fares are expected to range from 16 to 42 baht per journey.

Anon Sakburanapetch, the project’s engineering adviser, said the Grey Line will have 15 stations, with two connecting to the Airport Rail Link and BTS Thong Lor Station.

A study indicates that the financial Internal Rate of Return is up to 19.75%, a high-interest rate of return, Mr Anon said. The investment value is 27.8 billion baht, he added.

For the Grey Line project, the BMA proposes three investment models: Public-Private Partnership Net Cost, Public-Private Partnership (PPP) Gross Cost and Public-Private Partnership Modified Gross Cost, according to the BMA.

For the PPP model, the public sector is expected to arrange property ownership for the private sector to carry out construction, purchase rail carriages, and organise train operations. In return, the private sector will receive a share of the profit from the train operation, it said.