Do you have a sweater?

A common question I hear is "do you have a sweat?"  

This seems like a straightforward question, but it is actually tricky.... I don't always have a clean understanding as to why it is being asked.  It could be one of two reasons:

A). For the sake of modesty and respect, a sweat would be appropriate

B)  It is really hot and sunny out and, therefore, Thai people believe you should protect your skin by wearing a sweater

My problem is that It is not always clear as to why the question is being asked... I always want to be respectful and wear a sweater if it is respectful to do so. However, the appreciation for pale skin is not the same in the US as it is in Thailand.  Therefore, I am not as concerned about keeping my light completion as I am about melting in the nearly 100 degrees and humid weather.  

See, in Thailand pale skin desirable in the same way a nice, glowing tan is appreciated in America- and sometime one has to sacrifice for beauty.  I this case by sweating buckets.

So I find myself in a strange place, at times carrying a totally wet long sleeved shirt on my body, just in case it is culturally respectful to do so...