What is the current visa exemption policy for arrivals from the US to Thailand?

A user is confused about recent changes regarding visa-exempt arrivals in Thailand, noting that a friend from the US received a 90-day stamp instead of the expected 60 days. Other commenters clarify that citizens from specific countries (Argentina, Brazil, Chile, Peru, and South Korea) are eligible for a 90-day stamp, while US travelers typically receive a 60-day stamp with the possibility to extend by 30 days. They advise that if the friend is not from a qualifying country, they should visit immigration to have their stamp corrected.