Can I get a 30-day extension on the visa exemption while in Thailand or do I need to do a visa run?

If u come with a 60 day visa . U get a extension in Thailand. Plenty placed to get u 30 day extension . Even if u come with 30 day holiday .no visa required . U can get a 30 day extension on that. I am from Dbn . We just did the 30 just arrive. Then 30 day extension in Thailand. Cost 1900 baht . Now our time is up . So on 24 th Jan doing the V run . Hope that helps

Yes, at a local Immigration Office.