What should my friend do about his 5-day overstay on a visa exempt entry in Thailand before his flight home?

A user is asking for advice regarding their friend's overstay situation in Thailand. The friend entered Thailand with a 30-day visa exempt stamp that expired on April 4. With a flight scheduled for April 11, the options discussed include visiting immigration to apply for an extension at a cost of around 3900 baht or not doing anything and just waiting to fly home, which could result in a 3500 baht fine for a 7-day overstay. Comments emphasize the importance of avoiding any trouble with immigration before leaving.