Ask this group for a hotel recommendation in the area you want to go. Contact that hotel. Ask them for guidance.
I did my ThaiPass in January it was hell. I think part of my troubles were because the hotel wasn't familiar with their responsibilities.
Some people get there Thaipass back in hours, others, it can take weeks. I would recommend going with a hotel recommended by someone who has had a positive experience.
Bangkok Taxi's charge by time and by kilometre. There really isn't a fixed rate per distance. travelling 3KM during heavy traffic will cost more than the same route during light traffic.
If you have an eVisa you will need a print-out of that. I didn't see that in any of the paperwork requirements and I showed up, waited 1.5 hours, then they told me to come back.
If you are coming from the US.. Licorice and Google Voice.
If you travel anywhere, including Thailand. Try to be respectful of the local people and their cultures. 95% of the people on this site that have problems, have problems related to not having proper respect. It's not difficult..