If you live outside Bangkok, it's a good idea to get your yellow housebook at a friend's house in Bangkok. I tried to get citizenship in Khon Kaen but too hard. The process was much easier in Bangkok, however I had to get my birth certificate legalised then translated then verified. This was as for the citizenship process you need your parent's names on the yellow book. Also needed my parent's passport copies. You'll also need to choose a Thai name at the district office when starting the process of naturalisation, but you can keep your original name if you want.