Hi. I'm from Bangladesh. Now I'm staying in Dubai....

If somebody offers you a job in the UAE, he/she has to give you an offer letter issued by the UAE’s Ministry of Human Resources and Emiratisation (MoHRE). You can check the validity of such offer as stated below. Visit or tourist visa does not give you the right to work in the UAE. Working under visit or tourist visa may subject the person to penalties and legal liability
There is nothing called an independent employment visa. You are supposed to work for your employer. Your employer may give you a permit to work for another employer under approval of the MOHRE.
A residence visa cannot be processed for anyone while the applicant is outside the UAE. A residence visa can be issued only when the applicant is inside the UAE having entered the country on entry permit.