How soon can I extend my tourist visa at immigration in Thailand?

The individual is seeking information on how soon they can extend their tourist visa at immigration in Thailand, specifically noting that their current visa expires on May 3. They intend to extend it for one month before transitioning to an education (ED) visa. Responses indicate that the extension timing can vary by office, with some allowing extensions up to 45 days in advance, while others may allow only 30 or even 7 days. Additionally, it was mentioned that conversion from a 30-day entry stamp to an ED visa is possible, which might not align with the initial requirements stated.