Semplicemente, sali sul battello con bandiera arancione, paga alla bigliettaia quando la vedrai passare e scendi, mi pare, al Tha Chang. Comunque lo vedrai arrivando e la maggior parte dei turisti scenderanno lì. La fermata prima è il Wat Arun e, dalla riva opposta, il Wat Po.

My trip was included in a guided volunteer group. Don't have an answer however, you can contact them via email for a direct answer. I believe if you put their name in google and search Thailand specifically a web site should come up.

My understanding is that nighttime boating on the river is restricted for safety reasons, as many of the boats travel quite fast and also many do not have any lighting. In addition, it is hard for the poorer people, in their smaller boats, to see and allow for the wake turbulence from the larger faster boats

I use Thai regular people boat, it´s crowded, but cheap, fast...but is not good for older people and handicap. I dont have time in Bangkok to know better river transportation. I also use a klong boat to try to get to Grand Palace...no good, it´s an adventure...s....you see Thai hidden houses from luxury shopping malls in Siam area: I get this boat near Jim Thomphson silk museum, pay 5 euros each (tourist charge)...the intention was to run from traffic, but the pier was far from Grand Palace...we have to walk a lot..in confused areas. So next time is cheaper to get a taxi and if is not rush hour is also faster

You can buy it on the same pier. about 15bath to change about 50 cents  

Take the river taxi (orange flag) and enjoy the crowd and the shuffle. Don't bother with the Grand Palace (500THB). Go to Wat Pho instead - same location - cheaper (100THB) with the same temples and chedi. Smaller and not as tiring...

The express boat only costs 20 bath per person, tourist boat for 2 hours costs 1500 bath per person. Obviously it has more advantages such as visiting all the famous places, floating market, .... express boat drop you at each famous place but then you have to take a new one and pay money again. I paid 20 bath from the beginning to the final destination, just sit till the end. We went to other places by bus so just want to experience the express boat. It ups to you, if you have money, can take tourist boat for your family, otherwise, express boat and bus are still a good idea 😊