Traveled all day to get from Myanmar to Vientiane, Laos as soon as possible. I didn't want to spend anymore time in Thailand because my time is running out. I wasn't sure how far I could make it because I didn't know if there were going to be any night buses.
I took a shared taxi that I arranged through the hotel from Hpa An to Myawaddy at the border between Myanmar and Thailand. The taxi was just a private car that left at 09:00 and then arrived in Myawaddy at around 13:00. He dropped us off right near the border.
I changed all of my kyat to baht and then walked through the border and across the bridge to Thailand. The was an easy crossing with almost no lines. For the Myanmar border exit, there were no signs and the border guy came out of the office to call me in to the right place. It was on the left side and there were some sliding glass windows that were smoked and closed.
On the Thai side, there are different windows for different passports. I went to Window 14 for "Foreign Passport". I filled out the entry form and got right through. There were 2 or 3 people in line.
At the Thai immigration exit there was a motorbike taxi stand. I told them I needed to go to the bus to Phitsanulok and a lady taxi driver took me. She had to hold my big backpack between her legs while I wore the little backpack because it is a lot heavier and has all of my delicate stuff in it, computer, camera etc.
At the bus station, I bought the ticket for minibus to Phitsanulok which is about a 4 or 5 hour trip. The bus left within an hour and was full. There were multiple police passport checks along the way. On the second passport check about an hour into the trip, half of the people on the minibus got pulled off for some kind of visa problem. After that we had plenty of space on the bus until we picked up more people toward the end of the trip. We arrived in Phitsanulok after dark at about 19:00.
At the Phitsanulok bus station, they told me that the night bus to Khon Kaen leaves from a different bus terminal about 10 km away. The minibus that I was on probably went on to there but I had no way to know and the driver couldn't speak any English. I took a taxi to the other station and bought a ticket for the 21:10 overnight bus.