Victory Monument station was one of the most crowded, given its proximity to the anti-government protest stage being overseen by Thaworn Senneam, a leader of the People's Democratic Reform Committee (PDRC).
At the station, BTS staff set up a table selling 130-baht one-day passes to speed up ticket purchasing as long queues formed at the ticket vending machines.
One protester who bought a one-day ticket said he planned to visit several protest stages being set up close to BTS stations.
"It saves me money as I can travel around and there's no need to stand in a long row buying tickets from a vending machine," he said.
The Bangkok Mass Transit Authority has rerouted bus services to feed passengers to the BTS skytrain and MRT underground trains.
The changes are designed to help people negotiate the PDRC's Bangkok Shutdown, which is blocking six major intersections in the city.
Chaeng Wattana road, where the Government Complex is located, has also been blocked since before dawn Monday.