How do I get to the river from the Holiday Inn Silom and how do the river boats work ticket / direction-wise?

I tried taking a left onto Silom Rd, walked past Surasak, and it dead-ended into another road—had no clue how to reach the river from there.

Can I take a boat to the Grand Palace and how early do the boats run?

Could also use a refresher on taking a public boat down (or up) the river for pleasure—how far should I take it? (What stop?)