How do Covid visa extensions work in Thailand, and what are the considerations for applying in Pattaya?

A lot depends on your history. If you've had any non immigrant visa since you last entered Thailand you can't get one. If you've only had a tourist visa (or visa exempt) you can but must take the 30 day extension first. If you're on visa on arrival you can't get one. Plus at the end of the day it depends totally on the immigration officer you speak to, they have total discretion over whether to give you one or not

Advice is should be easy approval if not using them for several years. Chonburi/Jomtien/Pattaya very busy

At least for me, it’s been sort of both. Technically, it’s an extension, but in Bangkok, they treated my first application in January as if it were a conversion of my existing tourist visa to something new, so my sixty days started on the date of application. (Chiang Mai’s office also told me it’d be treated this way.) But I went in to extend again last week, and they gave me sixty days from when my current extension is due to expire.

I’m not sure about Pattaya, though.

Covid extension is for 60 days. Whether it’s added on to your existing stamp or from the day you apply appears to be office specific. Generally it would be from the day you apply, if it’s the first time you’re applying, but there are reports of some getting them added.

I’ll leave it to others regarding Pattaya as I have no knowledge of that office other than reading that it certainly has its quirks.