About half of the BTS commuters affected by train delays from June 25 to 27 have claimed compensation, according to the skytrain operator, Bangkok Mass Transit System Plc (BTSC).

CEO Surapong Laoha-unya said about 200,000 passengers have contacted the skytrain operator to claim compensation over extensive delays caused by signalling malfunctions.

It is estimated that about 400,000 passengers were affected by a string of malfunctions and the operator has offered up to six free rides and refunding options for passengers who have until tomorrow to claim compensation.

The skytrain serves about 730,000 commuters daily.

Mr Surapong said the company has been working to improve the system following the delays and passenger congestion in late June and will finish improving it by December or sooner if possible.

Anat Arbhabhirama, chairman of the management committee and member of the advisory board, said BTSC rushed to address the problem as soon as it and Bombardier Transport, who provides the rail control system, were able to identify the cause.

Mr Anat said the problem was caused by an overlapping of frequencies which forced the train system to suspend train operations occasionally which resulted in delays.

According to Mr Anat, Bombardier addressed the problem by replacing the transceivers, switching to a new frequency to avoid overlapping, and installing filters on the trains and train stations.

The installation of filters was completed at four stations, out of a total of 35 stations, where signalling malfunctions were reported.

The four were Siam, Phrom Phong, Onnuj and Bang Chak.

He said the Canadian firm also upgraded new software for its signalling system and made a test run, which was scheduled to take place during this long weekend.

Manpreet Mann, of Bombardier's product director network and cybersecurity team, gave assurances that the chance of signalling malfunctions causing train delays after the software upgrade is less than 1%.

He also expressed surprise that overlapping frequencies caused the malfunctions late last month, saying that 2.4GHz bandwidth is a widely used standard and the company had never experienced such a problem.