So you are not sure ?
I asked you because you seem very knowledgable about this.
IF you are stating your comment are factual and not just an assumption, I'll take your word for it... you are not known for BS'ing on this forum.
I am 100% sure that to drive a taxi/tuk tuk in Thailand, legally, a public service vehicle licence is required. That is a fact.
I am not sure about the answer to the other hypothetical questions that you asked regarding holidays and private use that I did not comment on.