Be careful, they won't tell you about the letter. You have to ask them to give it to you.. then you'd be able to process your fingerprints at the Royal Thai Police.
I have only 5 days left before my Visa expires (which makes the process impossible).
I'm currently visiting different lawyers who can request it using attorney's power and obviously pay more to get the fingerprints faster.
(as mentioned, it doesn't apply to all nationalities from what I've seen)
The website is down, "Required documents" section doesn't work for any category. I'll drop by Cheang Wattana this week and ask the Information Counter.
Meanwhile I'll get the wedding paper, Tambien Baan, Bank Statement, TM.86 & TM.87 ready with some passport photos.
I'll keep this post updated until the process is over.
It does when extended (every year) on the base of higher studies in a good university + I'm graduating and I'll request them to cancel it around early December as I'm done.