What are the requirements for extending a visit visa in Pattaya?

If you came on eVisa, you'll need a print out of that page.

I have found Pattaya to be unkind. You will likely need to make sure you have all your paperwork in order. Sometimes they require you file your paperwork a couple days before expiration of your current visa.

I use the visa service next to the immigration. They are pricier but at least the get the stuff done in one trip.