Here’s how you can get from BTS stations to go to the Mochit Bus Terminal (Also referred to as “Mochit Songg” (Mochit 2) or “Mochit Maii” (New Mochit).)
Basically the middle pink dot with the train symbol is the BTS Jatujak, and the pink line is how you can take a cab to the Mochit Bus Terminal where it can take you to many destinations in Thailand, as well as other cross border routes like Bangkok to Siem Reap or Bangkok to Laos or Vietnam.
The green line is the route where you can take a cab from BTS Sapankwai (one station before BTS Jatujak) and catch a cab to the Mochit Bus Terminal.
Note that you can ask the BTS booth officers which exit is the best to get to Mochit Station, even as a Thai I always ask which exit to leave to go to so and so place.
With this rough map, you should have an idea whether the cab is taking you to the right route. On a cab, with no traffic, it should only take less than 10 minutes. I won’t advise on motorcycle taxi, since it costs just as much (if not more) and I don’t feel safe riding them on main roads.
Another simple way is to print out the photo of the place with the address in the local language, all taxi drivers should be able to take you there easily. In this case, a photo should be more than enough.