Work on a railway line that would link the Gulf of Thailand and the Andaman Sea has hit a hurdle after opposition by residents in southern Thailand.

The National Environment Board on Monday rejected a proposal on the project after locals complained it had been drawn up without their involvement, as required under the law.

Its environmental impact assessment "was conducted without people's participation", local and environmental activist Wichoksak Ronnarongpairee told The Straits Times.

As a result, the board suspended it pending further consultations with the local community.

Dr Kasemsan Chinnavaso, Ministry of Natural Resources and Environment permanent secretary, was quoted by Bangkok Post saying: "After adequate information is handed to the locals and there is improved understanding, the (transport) ministry could re-submit the project to the board for consideration."

The plan calls for a railway line that would run over 100km from a port in Satun province by the Andaman Sea, to another port in Songkhla province by the Gulf of Thailand.

Initial estimates had put the cost of the project at around 50 billion baht (S$2 billion).

Officials had touted it as a quicker alternative to container ships now running between Europe and Asia, saving shippers the 1,000km journey around peninsular Malaysia - in other words, a land-based version of an idea to build a canal across the Kra Isthmus.

That idea never took off because of prohibitive costs.