Hanuman, granted life goes on as normal ... but AFAIK, the poster posted at the Chaophraya express boat booth at Sathorn Pier (Saphan Taksin), and I also personally experienced twice, all river traffic from Saphan Taksin to Thewet area will cease from 11:00 AM until 6:30 PM during the rehearsal and procession dates. Even though the procession rehearsal is actually conducted from the Thewet area down to Wat Arun.

Kalbozey,

Yes Thewet Palace or Thewet pier is along the route so it doesn't matter where you're coming from if the destination is off limit during the event.