@Rene *****
I wouldn't rely on anything you hear from Koh Phangnan or Koh Samui in regards to normal situations. Both of those immigration offices are rogue offices that don't follow many guidelines of Thai immigration. They're 2 of the only 3 offices in Thailand that don't allow tourists to apply for extensions until it's almost out of time. They just do what they want and they're allowed to do so. There are many, many reports of people that have been warned at immigration, showed a ticket out, and have absolutely no issue getting an extension in Bangkok, or anywhere else.