I felt the need to share the short but exhilarating solo trip I had from Don Mueang International Airport to Hua Lamphong MRT Station before meeting my friends in the hostel we were staying at. Scouring the internet for tips and train maps to get to the main city before the trip proved very helpful, but it took hours to do - so here's a shorter, more concise version. No one online seemed to have written anything comprehensive, so here I am!
While it might be a bit more of a hassle to get to the city center from this airport rather than from Suvarnabhumi International Airport (that's the one with the new Airport Link), it was still more efficient than, let's say, being a first-time tourist in Manila and your only decent option is to take a cab to your destination.
There are two ways to get from Don Mueang Airport to Hua Lamphong, at least, train-wise:
(1) Take a diesel train from Don Mueang Railway Station (right across the airport) all the way to Hua Lamphong Railway Station. This was my initial option, but as I've researched online, many travelers didn't recommend this route because the train arrival was erratic and it takes more or less an hour to finally get to Hua Lamphong.
(2) Take the newest A1/A2 airport bus (operating since the early part of 2013), get down at Mo Chit BTS or Chatuchak Market MRT, then ride all the way until Hua Lamphong MRT Station (conveniently connected as well to Hua Lamphong Railway).
(2) is what I did.
It's 30 baht a ride, and both of these routes like I said can take you to Mo Chit Station BTS/MRT station, the nearest BTS/MRT to the airport. It's quite useless to look for specific signs pointing you to where you're supposed to wait for the A1 or A2 buses, but follow the signs that say 'Shuttle' anyway and it'll eventually lead you to numerous exit doors that lead to the taxi bay and the main road.
I luckily found an A1 bus waiting at the exit near an airport security counter. It's an orange bus with A1 clearly readable by its door, and just to make sure, you can ask the nice security people that, indeed, A1 passes by Mo Chit BTS. I can't say for sure how often A1 and A2 buses come and go, but internet searches say that they frequent the terminal more than ten times. If you're unfortunate, you may have to wait up to an hour before the next one comes. It isn't a jam-packed ride, fortunately, and it takes about 30 minutes or so to reach Mo Chit BTS/Chatuchak MRT.
When the conductor finally tells you that you've reached your stop, walk down the sidewalk still in the direction of the bus route towards the pedestrian overpass, past some vendors and you'll eventually see the escalators leading down to Chatuchak Market MRT. It shouldn't be too hard to find!
Getting back to Don Mueang Airport is supposed to be easy as well (you basically do everything in reverse and wait at the opposite side of the road to catch an A1/A2 bus to the airport), but I took a cab instead for about 250-300 baht from Hua Lamphong MRT Exit 1 (using the meter, and including the toll fees).
I have no pictures, unfortunately, to guide you step by step, but hopefully this post helped anyway! :)