Welcome haloids, to the site.
There is an intro forum and perhaps you've already posted there.
In thailand i expect it's always warm and most always high humidity when it is "hot". You say hot, while I expect a heat stress index is high. High humidity does that. Regardless, a high ambient temperature versus a hot ambient temperature under high humidity are quite different with NO regards to an engine. (Your engine isn't sweating and evaporative cooling is not a significant factor). I consider hot as somewhere about 100F ambient. At 100F you might expect an engine oil temp approaching 215F. If its above that I'd consider a better lubricant. I use Amsoil. Oil temperatures exceeding 220 are cause for considerable concern.
I endorse a water wetter product, such as Proline, for keeping engine coolant significantly lower. I have observed, with an analog oil temp gage, at least a 15F lower temperature with Proline Water Wetter. Essentially a water wetter product diminishes or eliminate increasingly larger air bubbles from forming as the coolant approaches boiling. Proline says their product is best used with distilled water for the absolute best cooling. You should always use distilled water in any case. With the smallest of bubbles forming during the heating processes, the greater the water coolant is in greater contact with the heated surfaces; ands draining away the heat through the radiator.