I really wanted to write an answer to this, probably because very few people take this route. Most go from Bangkok to Pattaya, and many hire a private car, so what I found online was outdated or not detailed enough. Better to write my own.
2018.02.18
I traveled solo as a backpacker. My route: Bangkok → Hua Hin, boat to Pattaya, fly to Chiang Mai, then fly to Don Mueang and return directly to Nanjing. It’s easier to fly from Pattaya to Chiang Mai.
Okay, to the point.
In the morning I took the BTS to Victory Monument to shop at King Power.
After shopping and lunch, I remembered people online saying you could catch a minibus to Hua Hin at Victory Monument. I asked a staffer where to find a minibus; she told me the station here no longer exists and that I had to go to the bus terminal. I was baffled.
Then I checked: Bangkok’s four major bus terminals all have buses to Hua Hin. The Northern and Eastern terminals are more convenient. On Google Maps, the Northern terminal is right by the BTS with only a few stops, so I bought a ticket and rode to Mo Chit.
At the station, a bunch of “bus station” signs confused me again, so I asked a metro security guard how to get to Hua Hin. I spoke English; he answered in fluent Chinese: the old station is gone—take a city bus to the new terminal. He pointed me to a place and told me to take bus 3 or 77.
I followed his advice. The fare is 10 baht regardless of destination. While riding I asked the conductor when to get off for Hua Hin; she didn’t understand. A lady nearby chimed in with fast English I barely understood—not my English, but the accent. I thought she meant I’d missed the stop and should get off and go back one stop. Then the bus made a U‑turn and drove straight to the terminal—I realized she meant “get off at the next stop.”
Anyway, both bus 3 and 77 terminate at Mo Chit Bus Terminal.
The lady was very kind. After getting off she said “follow me” and led me, even teaching me how to pronounce “Hua Hin”. We crossed a street‑market alley—this is the terminal.
Friends, just search for the terminal name directly.
After thanking her, I asked terminal staff how to get to Hua Hin. Her English wasn’t good; she pointed vaguely toward the parking lot in the front square, meaning the vans are in there—find one yourself.
I looked and looked—no “minibus”, only sedans, and how could they depart from a parking lot? I asked a van driver; his English was good and told me to exit the terminal and go to the roadside.
Outside the terminal there were mostly taxis and one minibus not going to Hua Hin. I waited a bit, thinking maybe one would arrive soon.
After five minutes it felt wrong. Across the road was a parking lot with lots of minibuses—maybe it’s over there? I crossed, entered the lot, and staff told me I was in the wrong place and to turn left out the gate.
I followed his directions—turn left out the gate—and finally saw something that looked like a real station.
This is it.
Inside, I asked again and was told “Hall D”. Outside, several adjacent storefronts were labeled with letters: A, B, C, D.
Finally found it 
It wasn’t easy. I bought a ticket at window 2 for 180B, went straight in and boarded. The van was almost full; after two more passengers it departed.
Finding the right van took extra effort. Staff inside just pointed, and I didn’t understand what they meant. After asking twice they told me to look for “10”; I then noticed “10” printed on my ticket. I looked around—only huge numbers everywhere, mostly 70 or over 100. I went back to staff, and the driver directly led me to the van, pointing at the number on the vehicle: 10!
Back home we’d just draw a circle and write “10” in it. Here the door has lots of words and other numbers—hard to parse.
The numbers I saw are actually bay numbers.
It was quite an experience. The main issue was lack of clear info, so I’m sharing to help others avoid detours.
Backpacking isn’t easy—go easy on me.
Here’s where the minibuses are.
