Learn Hardcore Vietnamese: Tôi đi làm bằng xe buýt.

Because đi means go and làm means work. Combined, đi làm expresses the action go to work (i.e., commuting to your workplace). Saying Tôi làm alone means I work, which describes your job or profession, not the act of traveling to work.

What is the function of bằng in this sentence?

bằng is a preposition indicating the means or instrument used to perform an action. When discussing transportation, it corresponds to by in English. Thus, bằng xe buýt means by bus. You can also say bằng máy bay (by plane) or bằng xe máy (by motorbike).

Why do we say xe buýt instead of just buýt?

xe means vehicle and buýt is the loanword for bus. Together, xe buýt literally means bus vehicle. In casual speech, you might hear đi buýt as a shorthand for đi bằng xe buýt, but in formal or more complete phrases, combining xe with buýt is usual.

Can I omit Tôi and say Đi làm bằng xe buýt?