The tradition of offering alms to monks on boats is not seen so much these days. In the old days, when canals were the highways, it was more common. One place where you can still observe this is at Kwan Riam Floating Market in Minburi district of Bangkok. If you come at 7:30am on Saturday or Sunday, you can offer alms to monks on boats. Once finished, you can then have breakfast in this riverside market. They also do short 30-minute boat tours from here along Saen Saeb canal. It is a nice market, but it is not my favourite.