yes u can re-enter with a bussiness visa for one month...and u can renew it for an additional 2 months...no need for a noc.but u need to have a gcc rp as a engineer or manager.my freind was here last week .he came from dubai with a mechanical eng rp.and his sponsor canceled him from qaqtar like 6 weeks ago.now he is in germany and goin back tmrw..and im waiting to see if they will let him enter again as some people say that he need to wait 3 month between each visit to doha.