it was to do the translations, paperwork at Dept of Consular Affairs, documentation at Amphur and providing the interpreter and witnesses for the marriage.
I didn't go into it too much as I said, but wished I had later after about 4 trips to Bkk!
The ID card is completely different to citizenship, I agree life is too short for that. The pink ID card saves money at some attractions (you get the Thai price), acts as ID instead of using passport and I believe easier access to government healthcare. Probably other things as well.
It's a lot of running around going to different offices on different days.
I am opposed to agents for visas, but if I was to start this process again, I would pay an agent. I think I was quoted something like 8,000 baht and thought nah I will do it myself, but with hindsight 8,000 would have been a small price to pay.
When you get your passport translated, keep copies as they will be useful if you ever want a Thai ID card.
Definitely get an international driving permit before you travel. This allows you to obtain the Thai driving licence without doing the driver training other than a 1 hour video.
You also need a medical certificate, but you can get that at any doctors for about 200 Baht.