So this boat really does exist - I was on it a few days ago (at the dockside). It's a brand new boat built by a reputable company in Pattaya.
It's around 60 ft long and is designed to carry up to 65 people - very nicely laid out inside.
The bottom row of portlights in the hull has nothing to do with passenger seating.
I had a meeting with one of the owners and they hope to start a scheduled service between Pattaya and Hua Hin in September or October.
She's designed to travel at 20 knots, making a crossing time of 3 hours.
The fare is expected to be approx. THB 1,200 each way but it's not definite yet.
The logistics on this side have still to be finalised.
As and when I get further info, I'll post it here.