I registered on their app a few weeks ago and when trying to schedule an appointment, according to the app, they were fully I went in person and received a it for 10 days later
Online for foreigners doesn’t work. It lets you register, but as you saw, all slots are full. Maybe in future? You need to go in person and book an appointment, for Banglamung. The Rayong DLT allows some walk ins
Looks like you’re American, so it will be 800k. When you arrive, open a Thai bank account and deposit it. Needs to always be in for the 2 months preceding your 1 year extension.