You can first go to China embassy in Abu Dhabi(https://www.travelchinaguide.com/embassy/arabemirates.htm) or China consulate in Dubai to enquire whether you can apply for Hong Kong visit visa here. As I know, almost all Bangladeshi need to send their application to the Hong Kong Immigration Department directly if they live in Bangladesh. The China embassy in Dhaka only accept Hong Kong visa application from a few applicants who are Celebrities in Bangladeshi society and business circles or Employees of famous large-scale enterprise in Bangladesh.