How do I transfer my visa stamp after losing my passport, and can I do it in the afternoon due to my morning Thai class?

Unless you have your old passport in which case they will transfer the visa over easily.

you are most likely going to have a problem :/ That's because the way it works is

If you're on a 30 day visa exempt entry they can look up your arrival information,

If you're on a 30 day extension off a 30 day visa exempt entry or a tourist vsia they can look up your information,

BUT

Sometimes if you're on the original entry from the 60 day tourist visa you got from a thai consulate they can find your entry history BUT can't prove you had a single entry tourist visa. Either they make you show your receipt from buying it OR they send you to the ministry of foreign affairs office (out near the immgration building on Chaengwattana) and they contact the consulate that sold you the visa, get them to fax proof and you use that to go get a 30 day extension on it.

They stop giving queue numbers out at 3:30 out at Chaengwattana, BUT if you get a queue number you will be served today. I'd say blow off the thai class and get your permission to stay sorted out FIRST.

And what type of stamp were you on?