Legal Or Illegal????

I have this question in my mind for quite a long time already; but it just I don't have time and opportunity to look for the answer. Coz during the time when I'm operating the AV equipments in some D&D events(D&D=Dinner & Dance) I always see the catering,hotel, restaurant, banquet hire some people for "Part Time Waiters/Waitress"
Yea..... there is nothing wrong with hire for work as part time. I myself also work for people for part time too.. Part Time is good.. Is freedom and not need to see the boss face either he mad or happy.
Some how I believe many people after graduated until now still haven't find a job. So part time somehow was some people favorite job:like me!!!
But the question is.... Does Foreigner are allow to work as PT too?
I see a lot of Indons and Pinoys mostly hired by part time for the Banquet or Wedding Dinner. 
But I really don't understand; It that legal? As far as I know if this people come here using Tourism Visa, under Maid's Kota or ant other Kota saja lah. they shouldn't work under any other company or employer right??? ( correct me if I'm wrong) Even my own maid also cannot goes to my shop to help clean up the floor ah!!!! If kana tangkap... Jialat man!!!!
I tell you don't play play this people... They can earn more then thousand dollars per month... Bila-bila can earn more than you and me some time. And they all have contact with the local restaurant, catering and hotel one. Just one call only and they can call up all the gang and come to work for you as PT with your D&D liao. Seriously I just interview an Pinoy guy that he told me he been staying here in for 1 year plus already and now he work for 5 restaurant/hotel/catering for PT only... one month basic income is 1k but coming next the 2 months Puasa holiday he going home coz not much event held. 
You see.... every way is money it just that you want to get it or not. You don't want to take it so other people come here and Sapu it lah!!! 
If you don't believe it.... next time you ask them when you attend a wedding dinner at any hotel or those function hall!!! 
Anyway... this is the best and safe illegal work here. You know why??? Coz it won't happen when  you see people come to tangkap them in the middle of people's wedding or function!!!