"不用太厚的衣服" 的英文表达可以是 "You don't need to wear thick clothes." 或者 "You don't need to bundle up."

这个表达的来源可能源于人们在寒冷的天气中穿厚衣服以保暖。"Bundle up" 这个短语的意思是穿得更厚，也可以用来指穿厚衣服保暖。

下面是一些例句：

It's not that cold out, you don't need to wear thick clothes.
You don't need to bundle up, it's going to be warm inside.
I'm not going to wear a coat, I don't need to bundle up in this weather.
It's not necessary to wear thick clothes today, the weather is mild.

中文翻译如下：

外面并不是很冷，你不用穿太厚的衣服。
你不用穿得太厚，里面很暖和的。
我不打算穿外套，这种天气我不用穿太厚的衣服。
今天不必穿厚衣服，天气温和。