Passengers suffered long queues at two major BTS Skytrain stations on the Sukhumvit route on Thursday morning, although a rail official said there was no problem with the service.
At 8am, passengers crowded Udomsuk and Onnut stations and long lines overflowed to street level.
Several passengers posted messages on Jor Sor 100 Facebook page that they waited for trains for more than an hour.
Passenger Phatthira Karnpakdee said she waited at the Udomsuk station from 8am and could not get on a train after an hour although four crowded trains passed.
A BTS official said there was no fault with the service and the congestion was probably caused by the high volume of passengers following morning rains.