How can I extend my 30-day tourist visa exemption in Thailand, and does visa run still work?

Hello everyone,

I'm new in the group and arrived in Bangkok from France a couple of days ago with a 30 day tourist visa exemption. However I doing a training for more than a month an need and extension. I'm wondering whether visa runs still works and in your opinion whether there's any destination to run to more convenient than others. It looks like I cannot make the extension at the bkk immigration bureau as they're only opened weekdays :-(

Thanks so much for your help

Cheers

Nico