给老板的thank you letter写些什么

Thanks for helping me on the case during your busy day.

要写你在他/她帮助下获得的成绩。
老板的工作就是这个。。。

Dear boss,
I write this letter to express my grate to you for the favor you have done me, especially when you're very busy during the period.
.....
Yours truly.
Mr A.