What steps can my friend take to correct her mistaken visa stamp upon entering Thailand?

A user is seeking advice on how to fix a mistake made at Phuket airport where her friend, who holds a non-B working visa, was mistakenly stamped with a 45-day visa on arrival. Commenters suggest that she should return to the airport or the main immigration office to get the stamp corrected. There is also advice on ensuring that entry stamps are checked thoroughly at immigration to avoid such issues.