Yes you are right and I did mis-say AAT I did mean high. But thats for the better part of the day.A high of 120F is rather different from an "Average Air temperature of 120F" and you should probably report that reading so you can replace Mar Hong Son for the highest recorded temperature in Thailand.
I rather think that you may have extra heat radiating up from the ground around your house that is increasing the local temperature.
Actually the ground in the shade is rather cool compared to the air temp. The concrete post the thermo unit is on (About 1.5 meters from ground) takes on the air temp.
Starting February now 3 weeks and I'll post Pics