Does Bangkok have a subway?
Yes, Bangkok has both a Skytrain (BTS) and a subway (MRT), even if the latter one has lines above the ground nowadays.
The BTS and MRT are often cheaper, faster, and more convenient compared to using taxis (yes, Bangkok can be very congested). The lines are separated and have different ticketing systems. Therefore, you sometimes need to change from the BTS to the MRT if you want to reach certain areas.