Not sure about the Skytrain...but I think the Marriott shuttle boat stops about midnight so you would have to rely on taxis after this time to get you around. As for the Marriott...have stayed there on four occassions...have stayed in other hotels and in other locations within Bangkok but prefer the river and the Marriott is one of the more reasonably priced hotels on the river. Also has a great pool area for a city hotel and you get a balcony.