Travelers in Bangkok can now check in their luggage when boarding the city's train-to-the-plane for flights on certain Thai airlines, with most carriers opting out of the service for now.

A high-speed train link from central Bangkok to Thailand's main international airport, modeled after Hong Kong's hyper-efficient Airport Express, opened in August after years of delays but without baggage check-in service.

On Tuesday, the Airport Rail Link to Suvarnabhumi Airport launched a service that enables passengers flying national carrier Thai Airways and Bangkok Airways to get boarding passes and check bags at the train station, said spokeswoman Prapaporn Kocharin. Luggage can be checked from three hours to 12 hours before departure times.

Prapaporn said all airlines were invited to use the service but so far only the two carriers had accepted their offer, leaving 21 of 28 check-in counters at the capital's Makkasan train station empty.

"We are expecting more participants in order to extend these free services to more passengers," Prapaporn said.

The express trains connect Makkasan station and Suvarnabhumi Airport in 15 minutes and cost 150 baht ($5) per trip. Trains run every 15 minutes at a maximum speed of 64 miles (103 kilometers) per hour.

A local, commuter line that runs parallel to the express train takes about 30 minutes and costs between 15 baht and 45 baht (45 cents and $1.50). Baggage can be checked in by passengers using express or local trains.

Critics of the train link say Makkasan station is inconveniently located and not connected to other mass transit lines.