So Pattaya in May ?

[thaiophilus]

Not all polyester is the same. Modern "technical" fabrics are mostly synthetic, and designed for extreme weather.

Looking at one of my Rohan shirts, it's 57% polyamide, 43% polyester, feels like cotton but wicks the moisture away so it doesn't develop sodden sweat patches.
It can be washed in the shower, drip-dried within a few hours and doesn't need ironing.