By Pratch Rujivanarom
ARL reported on its Facebook page that trains were arriving every 12 minutes during rush hour because four trains were undergoing major maintenance.
The congestion was reported to be easing by around 10am.
The reduced service had led to overcrowded platforms at a series of stations, and access to the platforms at Lat Krabang, Ban Thap Chang and Hua Mak stations had to be restricted.
Passenger queues spilled over into the ticketing areas.
Complaints filled the social media, some people saying they waited much longer than 12 minutes, in some instances more than an hour, because carriages were too crowded to board.
User comments on the ARL Facebook page included suggestions that it buy more trains to increase capacity.
ARL apologised but said there were no plans to buy additional trains soon. It said replacement parts were on order for the trains currently out of service.