Henry Durrant Two reasons. One, because she is volunteer and may not be renting a house or living in a hotel, and therefore, house owner may or may not have the knowledge of TM30. Second, since it's her first time, it's better to be cautious. Know what it takes, do and don't.
If I were you, I would get TM30 first, work permit, and start working on papers needed for extension ASAP, particularly the photo required in the application.
What Mr. Tod Daniels said is a counter located before immigration checkpoint and in close proximity. It may not
have an officer on station, as it is sometime the case at Chiang Mai Airport. But if you stood in front long enough, someone will come and take care of you.
My answer to your first question is different. Applying for Re-Entry couple of days ago, my answer to the first question is the last visa extension. I was told this by an Immigration officer at Chiang Mai Airport.