How soon able to extend visa exemption?

Hi all,

US visitor here planning on entering Thailand with a 30 day visa exemption. I'd like to extend the exemption for another 30 days as soon as possible after landing, because I have a 45 day meditation retreat so I want to avoid leaving to do a visa extension run later. (I messed up by not applying for the 60 day tourist visa on time)

I've heard that the Bangkok and Chiang Mai immigration are the most relaxed and can extend visas as early as the day of landing, so you don't have to wait a week before visa expires..

Two questions then:

1) Does that sound right - that it's possible to extend a visa / exemption within a few days of landing?

2) What are the embassies in nearby countries that do the fastest tourist visa processing? (Also considering this option)

Thank you in advance 🙏