Sorry for the lack of updates. Wanted to get a bit of data before posting again. Seems this is quite a sensitive subject.
Yes I get 20c was way too low. You have to understand I just arrived from a country where it's 0c, so the temp jump and humidity was a lot for me. The aircon is now set at 26c and this seems more than acceptable.
Problem is by my calculations the bill is still going to be ridiculously high for where I live...
Over the last 24 hours (with the aircon set at 26c) the electric meter has gone from a reading of 835 to 848, so 13 units of usage. That would mean at this rate my monthly bill will be 3,200 Baht (paying 8 Baht per unit). But for arguments sake, assume I was paying 5 Baht per unit, I'd still be looking at a 2,000 Baht bill, which for a studio apartment with no washing machine or dishwasher and just 1 AC unit seems very excessive to me.
I did the test where I switched absolutely everything off and the meter did indeed stop spinning. Left it for a decent period too and nothing was shady. So at this point aside from moving I'm not sure what to do. I'm using the bare minimum any normal person can. My fridge is set to the most energy efficient setting, I don't leave lights on, my TV is mostly switched off, and I only run the AC when I get too hot. What more can I do?
Unless there's some sort of advanced modification that's been done to use more electric (when the AC is switched on), I'm lost as to why my usage is so high