It looks like you're from the Netherlands, you don't need a visa, you can enter on free 60 day visa exempt entry stamp, and you can extend this once an additional 30 days at immigration for 1900 baht
a single re-entry is 1000 or 3800 for multiple, available at your immigration office or an airport with international flights such as DMK, CNX, BKK, HKT.
I don't know that one really needs any paperwork from the MT center, depending on the consulate possibly just show that you've enrolled and paid along with their name, address, and registration certificate number etc.