Confused about the difference between a thermostat, probe thermometer, and infrared thermometer

Specifically when it comes to measuring the warm side. I know an infrared thermometer can measure anywhere, and a probe thermometer can also measure the ambient temperature, but if I’m just needing to track warm side temperatures can I just use a thermostat? My snake’s UTH doesn’t seem to be warming like it used to, but before I get a new one I’d like to make sure it really is malfunctioning. I’ve seen an infrared thermometer recommended for this, but right now though all I have is a dual thermometer/hygrometer stuck to the back of the tank, towards the bottom. I know I need more than just that, and I know I also need a thermostat, so could I just get a thermostat to monitor/adjust warm side temps and use my current thermometer to measure the ambient temperature and humidity?