When I bought my first GS in bangkok, as I didnt know the way out, just rode to the Southern Bus terminal, and followed the first bus going south, that way dead easy to get out, and only 1 set of traffic lights for 100 kms.
and if you have a GPS then, can just put in way points as you are travelling and you can save your track as well.
BUT... I dont know if you are aware that bikes arent allowed to ride along the middle section of road, we have to stick to the side road/slip road. So here i am following the bus out of bangkok and i get pulled over by the traffic police waiting on side of road. i am polite and tell Mr Plod that "I not know the way out of bangkok and must follow bus to Surat Thani" So he wants to charge me 1,000 baht, and I think this is thailand might as well try and bargain and I managed to knock him down to 500 baht, which I thought was good.
Then on speaking to guys living in bangkok, asking them what they do, and firdtly if stopped you only pay 200 baht, also they just sit on 120kph, ride in the outside lane, (normally 3 lanes), and pretent ou havent seen the copper, just look the other way, its very rare they will chase you as 1) they wouldnt be able to catch you, and 2), whilst chasing you they will mis catching other guys on bikes