This is the 5814th most frequent Russian word.
рабочим
"Рабочим" - "worker" (instrumental or dative singular form of "рабочий").
The word "рабочим" is used here in the instrumental case plural form of "рабочий" to indicate a group of workers being the object of gratitude.
Я благодарен рабочим за их труд.
I am grateful to the workers for their labor.
Here, "рабочем" is the locative (prepositional) case singular form of "рабочий" used to describe a workplace as the context of the action.
Он получил новую должность на своём рабочем месте.
He got a new position at his workplace.
In this instance, "рабочим" is the instrumental case singular form of "рабочий" describing a process associated with work or functioning.