The Supreme Court overturned the annulment of an arbitration award, which ordered SRT, under the purview of the transport ministry, to pay the amount to the Thai unit of Hopewell within 180 days for wrongful concession termination.

Hopewell and SRT did not immediately respond to Reuters request for comments.

The Transport Ministry, in a statement, asked SRT's board to consider what steps it would take next, based on the court order, so it could propose them to the country's cabinet.

In 1990, the Hong Kong-based infrastructure firm started constructing the Bangkok Elevated Road and Train System (BERTS), but the project was delayed and eventually terminated following the Asian Financial Crisis.

Physical work on the scheme was halted in the middle of 1997 as project funding ran dry after Hopewell had spent almost $600 million on the incomplete project.

The Thai government formally terminated Hopewell's concession to build and operate the project in January 1998, citing unacceptable delays.

With only about 10 percent of the project completed, massive concrete slabs still line Bangkok's Vibhavadi Rangsit Road.

(Reporting by Panarat Thepgumpanat and Chayut Setboonsarng, Editing by Sherry Jacob-Phillips and Kirsten Donovan)