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.
To the South
Near by skytrain's station "Wongwian yai" there is a rail road station (13.724441, 100.491312). Frim this station yuo can take a train to the last stop "Maha Chai" (13.545823, 100.275569). There are a lot of trains from 5 a.m., price is 15 bat =0.5$.
To the North
Option One: 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
Option Two: From central rail road station (13.739418, 100.516694) you can take a train (every one or two hours, ฿15) to this station (14.385274, 100.598595) or sometimes the train will stop at the next station Map Pgra Chan (14.402356, 100.632265), but you can easily hitch-hike from the village to the main road.
Option Three: Get to metro station is Wong Sawang on the MRT's Purple Line, from where you'll have to get out of the station walking in a southeast direction, to the big intersection of Wong Sawang Rd/Ratchadaphisek Rd. Turn left and follow Ratchadaphisek Rd until the intersection right at the canal/river, where you have to turn left again. After a few metres, you'll already see the hospital.
Facing the hospital's main car park/entrance area, turn right and pass it on the right, entering Sai Sin Alley (you can see a 7-11 convenience store); it's the only road branching off before the expressway bridge. Follow the road until the crossroad and turn right on the second road, as the first one leads back to an intersection near the canal/river. From there, you'll already see a road running along the side of the expressway. Enter and follow this road; there's no pedestrian walkway so you'll first walk on the grass on the left hand side, then along the edge of the road.
Eventually, as the road rises, you'll see that it becomes the leftmost lane of the tollgate, where you can simply pass on the left hand side on the pedestrian walkway that starts shortly before the gate. Right behind the gate is a covered walkway (link to Google Maps), where a lot of people going North stop.
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.