Bangkok's BTS sky train runs within 1.5 kilometres of San Phawut pier, next to Wat Bang Na Nok in Bang Na. To reach the pier, take exit #2 out of Bang Na BTS station and catch a taxi to tha-ruea san-phawut. Or, if wanting to get there on your own steam, walk straight out of exit #2, take a left onto San Phawut Road and walk for some 1.5 kilometres to the pier at the end of the road.
If wanting to enter the peninsula from Khlong Toei pier, Thong Lor or Ekkamai BTS or Khlong Toei MRT station are the closest you can get by train, but these are still some 4-6 kilometres away so you'll probably want to take a taxi from any of them.
Local buses run frequently between 06:00 and 20:00 from Khlong San in Thonburi to the centre of Phra Phradaeng town; the buses are yellow and can be caught from any southeast bound bus stop along Charoen Nakhon Road. There's also a local bus that departs regularly throughout the day from Victory Monument (it's bus #140).
Once in Phra Phradaeng, switch to a blue and white local bus headed to Bang Kachao pier, which run all day until 18:00. If going to Bang Nam Phueng, ask to be let off here and it will be a little over a kilometre to the weekend market or any of the places to stay.
Small songthaews also shuttle passengers from Phra Phradaeng town to Bang Nam Phueng village, running more frequently on the weekends.
The easier way to reach the peninsula is by boat. From San Phawut pier in Bang Na, mint green skiffs transport passengers from the white pier at San Phawut (on the left if facing the river), costing 4 baht per person and running from 05:00 to 21:00. This ferry drops passengers at Wat Bang Nam Phueng Nok pier in Bang Nam Phueng village, from where Bangkok Tree House is 300 metres down a path to the left if looking away from the river. The weekend market is reachable by motorbike taxi or on foot.
The red roofed pier at San Phawut (on the right if facing the river) has longtail boats to Tha Luan pier or Homestay pier (at Bang Nam Phueng Homestay) for 15 baht, but you'll need to specify to the driver that you want to go to Homestay pier upon boarding. A few motorbike taxis are typically found at Tha Luan pier, which is at the end of Wat Bang Nam Phueng Road and not far from the weekend market. This is also the closest pier to Py Aoy Longstay and Phuengnang Homestay.
If wanting to head straight to Petchahung Road, take a taxi from Thong Lor or Ekkamai BTS stations or Khlong Toei MRT station to Khlong Toei pier (Tha Khlong), from where longtails are available 24 hours per day to shuttle passengers to Bang Kachao pier. If taking the regular longtail ferry the cost is 10 baht per person, but if arriving late or wanting to leave immediately it's 40 baht for one passenger, 50 for 2-3 and 60 for 4-6.
By far the most popular way for both travellers and locals to get around is by bicycle. Fifty baht seems to be the going rate, and they can be rented at Bang Nam Phueng Homestay, Py Aoy Longstay, a stand near Bang Kachao pier, and the Joss Stick House near Bang Nam Phueng market (although we were told it would be 100 baht per day there). Both Bangkok Tree House and Phuengnang Homestay offer bicycles to guests for free.
It's easy to get lost while bicycling on the raised walkways, but if you bring a compass and a map you should be fine. The peninsula isn't all that big and Petchahung Road is an easily found central reference point.
Though few seem to take advantage of them (everyone we asked seemed surprised we were asking), motorbikes can be arranged through Phuengnang Homestay for 300 baht per day.
Yellow-vested motorbike taxis are easy to find in all but the most out of the way corners of the peninsulas.
Traditional human-powered rickshaws are still found throughout the area, although they tend to stick closer to Phra Phradaeng town. A rickshaw can take you all the way from Phra Phradaeng town to Bang Nam Phueng market for 150 baht, not a bad deal given it's a pleasantly slow 20-minute ride from city to countryside.