Not sure I understand the exact logistics of your travel plans but if you are traveling on an Israeli passport then you are granted a 30 day tourist visa exemption arriving at an international airport in Thailand.

I do not believe you could convert to an Ed. Visa in country, but I am far from an expert. I think you'd have to leave Thailand, and then re-enter on your Ed. Visa. Maybe best to check on the ThaiVisa forum?

http://www.thaivisa.com/forum/forum/...-work-permits/