From the courthouse in Samut Prakan city (commonly known as Paknam) to the prison, it is about 30 kms. Just drive along Sukhumwit road past the Ancient City and towards Klong Dan. From the Paknam Market area you can catch buses to Klong Dan (20 baht) and also a minivan (30 baht). Unfortunately, everything is written in Thai so you will have to ask someone which bus is for Klong Dan. The colour of the bus is yellow, white and green stripes. A taxi from Paknam would be about 175 baht. There is no direct bus from Bangkok to the prison. You would have to catch a bus to Paknam first and then change. From the last stop on the Sky Train, at On Nut Station, a taxi would cost about 120 baht to Paknam and takes 40 minutes. 

The journey by car is about 40 minutes. By bus it would be about one hour. About half way, the road goes from four lanes to two lanes. It runs straight for most of the way parallel to the Gulf of Thailand. The sign for the prison is only written in Thai. What you need to do is look out for the point where the road becomes four lanes again for a short distance. You will then see a steep bridge on the left and the prison watch towers beyond. In the satellite picture above, you can see there is another road that comes down from the Bang Na-Trad Highway. You could take this if you want to bypass Paknam. However, you do have to zig-zag a little.

If you are driving yourself, be careful as you drive up and over the bridge as you won't see the oncoming vehicles. On the other side there is a guard post. In the past, you had to give him your driver's license. They may have stopped this because sometimes the guard gave back the wrong license. If they start doing it again, check first they give back the right license! If you came by taxi, you will then be dropped off here. The big building in front of the roundabout is the administration building. To the left is the waiting area for visitors. That is where you want to go. If you find you have a couple of hours to wait before your visit, walk down to the left where you will find the canteen.