@W**
it lists four stamps and the first one, ผ.60, is the most common one that most countries get. It doesn't list an exempt unilateral 90 day stamp I don't think but ผ.ผ.90 which is the Brazil/Korea one. ผ.ผ.30 I think is the bilateral treaty Russia one.
It does mention special screening for certain nationalities that are involved in problems, but as far as I can see the categories of stamps listed are just all the exempt stamps, not one in particular.