Can I extend my stay in Thailand if I entered by land on a 30-day visa exemption?

Yes, you can get a 30-day extension at the immigration office for 1900 baht if you entered Thailand under the 30-day visa exemption, regardless of how you entered the country. Alternatively, some suggest obtaining a 60-day tourist visa first, then extending it for another 30 days, and afterward entering again on a 30-day visa exemption to extend once more.