What documents do I need to extend my Non-B visa at the immigration office in Thailand?

Hi guys, I’ve a multiple non b visa (until October) with the stamp valid until the 13rd of April. Since I cannot exit and re-enter the country as planned and get 90 days I’m supposed to go to the immigration office.

Do you know which documents I need to bring along other than the Passport, embassy declaration (already got it), 2 photos and 1900 baht for the extension of 30 days? Or do you know any good visa service agency that could help going instead of me there?

Thank you 🙏