There is a boat tour at the pier front of Wat Poramai Yikawat Temple. ( the same pier you ride ferry from Pak Kret). The price is 40 B for person, The boat look like in the pic, will take 2 hour. about 70 passenger in the boat. There's a guide explain the area but speak only in Thai language. The boat will stop at some shops at the canals of Thai sweet dessert to see how they cook Thai dessert and you can buy it. The boat also stop at some temples and floating market. I think it was great to see the river and area around the islet by boat but I felt too crowded on boat and the tour stoped by too many souvenir shops. ... Well it's still worth 40 Baht for 2 hour anyway ..
To me the best way to enjoy Ko Kret is walking. You can make a leisurely walk along the elevated walkway which rings the islet, wander through the villages to see lifestyle of locals and Mon people. Many family-run shops along walkway. By foot, you can enjoy things better than other mode traveling but !!! The distance of walkway rings around the islet is about 6 km and from my experience only 2 km most visitors give up, me too, ;-) the left distance to go, better find other ways; ride a bike, ride a taxi boat or even taxi motorbike.
From Pak Kret the land to Ko Kret islet, you must ride a boat across the river which take only few minute. ( fare = 2 B ) Actually you can get to Ko Kret islet by buying a package tour from Central Bkk but will be a lot cheaper my way but a bit adventure, not too difficult....interesting ?
Fisrt, you just take bus no 166 as the tip above to Pak Kret, (near the Pak Kret pier, but not the pier to ride a boat to Ko Kret) You must look for Jusco small departmentstore you will walk in the soi (sub way) next to the mall, go to Wat Sanam Nau Temple. But it can be so hot by day so I took motorbike taxi for 5 B. to the pier within the area of Wat Sanam Nau Temple. Walk to ferry pier where you can ride ferry across the river to Ko Kret, ferry look like on my photo.
As I said the distance all around the islet is about 6 km and can be so hot by day even a lot shade along walk way. I think the interesting things such as cultural centre..shops, local restaurants, only in first 2 km, the left will be mainly living area, villages so you can ride a bike tour around for the left. This rental shop is at front of Wat Sao Thong Thong. It's 40 B to ride (no limit time).
To go to Pak Kret, Nonthaburi (Pier or Market ) very easy by take bus no 166 from Victory Monument about half hour you will get in Pak Kret. From Victory Monument the bus will get in expressway all the way to Pak Kret. The look of bus like in the picture, fare less than 20 B.