Is it correct that that stamp you get when you enter the country that allows you to stay for 30 days is called visa exempt? And is it also correct that you can extend it by another 30 days (for 1'900 Thb) at any immigration office (for example at Chiang Mai)?

I'm asking because if I read about visa stuff on the website of the Thai Consulate in Switzerland, it says that if 30 days are not enough you MUST have a visa, you get in advance, valid 60 days. It's nowhere mentioned that you can extend that stamp. Do they just want to sell that very expensive visa (150 Euro) or is it really not possible to extend the stamp? Switzerland belongs to those countries that should have that possibility. Can anybody help? Thank you 🙂