Not advocating anything but just reporting our experience yesterday at Phuket immigration in Phuket Town getting a 30 day extension.
50% of people were wearing shorts and flip flops.
TM30 was NOT needed, only needed copy of passport (2 pages signed) and new passport sized photos and TM 7 filled out.
Around the corner they take photos and make copies. Very easy.
TLDR : Answer Summary
The experience of extending a 30-day visa in Phuket immigration highlights that a TM30 form is not needed. Applicants are required to provide a copy of their passport (two pages signed), recent passport-sized photos, and fill out the TM7 form. Many attendees were casually dressed, and it was noted that different immigration offices have varying degrees of strictness regarding dress code.