Bangkok (กรุงเทพมหานคร, Krung Thep Maha Nakhon) is the capital of Thailand. It's a pretty big sprawling city yet it's quite easily managed once you get your head around it.
Trains in Thailand are very very cheap, so many hitchhikers opt for heading down to the main train station and catching a train to some place outside of the big city. Another option that can seem a bit more stressful, but is perfectly possible is to start hitching right from the center. If you're standing in a decent enough spot someone should stop within 10 minutes.
To the South
There's a bus with the number 68A that leaves from near Khao San Rd. and will drop you off right near the highway somewhere south of Bangkok if you ride it to its last stop. To find it, go North from the Eastern end of Khao San Rd. until you come to a roundabout. On your right, there should be Thanon Bowon Niwet (Bowon Niwet Rd.) where bus 68A begins in front of the big Wat. Once you've arrived at the last stop, keep walking in the direction you've come from and you'll hit the highway very soon. The exit of the resort there appears to be a good spot. (NOTE: as of August 2017, it appears that there is no "68A" bus. The 68 bus is free; it leaves from the same location described; and it definitely goes in the right direction. However, if you ride it to the end, you'll end up in a very urban area with no good places to hitchhike.)
To the North
Highway 1 heading north starts at the Victory Monument. Two bus lines will take you a good way up the road: 39 and 510. Get off at the last stop Thamassat University, Rangsit Campus ( มหาวิทยาลัยธรรมศาสตร์ รังสิต). Bus 39 doesn't depart from the bus stop listing its number, instead it stops at a different part of the roundabout. here if user Jans recalls correctly Link title
Eating and Sleeping
There's a Sikh temple near Sukhumvit MRT station [13.73733N, 100.5611E] where you can get free food between 9am and 11.30am and 6/6.30pm to 9/9.30pm. To find it, locate the exit of the station that is in the North along Thanon Montri Rd., turn right and walk some hundred meters. The temple is on your right, you can recognise it by the Indians dressed in white that are hanging out on the square before it. Keep in mind that you should cover your head (also as a male) and also show your reverence by going into the room on your right and bowing to all the spiritual men and all the pictures of spiritual men in this room. When you leave it, you'll be rewarded with a sweet :-) afterwards just hang out in the main hall until somebody notices you; they'll know you're there for the food. After the meal you're expected to wash your dishes. In this temple, there's always people sleeping as well, so if you charm them they might let you crash with them for a couple of nights as well.
Bangkok has an extensive system of buses and metro lines (not to mention the countless taxis, mototaxis and tuk-tuks that plow the streets). The metro lines are pretty cheap if you're used to European standards, and at least the MRT can be blackridden. For every journey you buy a black plastic electronic coin that you hold against the entrance gate to open it for you and that you drop into the exit gate when you leave the system again. Note that the coin will notice if you travel for more stops than you paid for. Now for travelling free (a bit harder to do with a big backpack) you just slide yourself through the entrance/exit gates with another person. Ideally this will be somebody you know because you have to follow a person quite closely and unless it's rush hour the random Thai person unwittingly helping you might be freaked out by your sudden presence so closely behind them. The entrance gate will also notice when two people pass through it at once and will beep loudly, but if you just pretend nothing happened, you'll most likely be fine as according to actual experience :-) After all, you're a tourist and if anybody should stop you just talk to them confusedly in English. The exit gate doesn't make any special sounds when two people leave it at once.
There are SOME red buses throughout the city which are free. Before boarding a red bus, make sure you see the word 'free' (ฟรี) written somewhere on the front of the bus (sometimes there is a blue circle with the word in white; other times it is at the end of a sentence). Just hop on and hop off wherever you please. Bus 15 is good to see Khao San Rd, Siam Shopping district, Ratchadamri Road, Asiatique Market and everything in between. visa:Bangkok