If you can't afford a thermostat, then sell your snake to someone who can. A thermostat is required and the FIRST thing you should be buying before getting a snake, or you risk (and you've seen it now) severe burns and injury to an animal that is supposed to be in your care.
If you can't care for an animal properly without causing it harm because it's out of your budget, you need to sell it.
A hydrofarm thermostat, which is $30 and gets the job done at least for a few months.
https://www.amazon.com/MTPRTC-Contro...arm+thermostat