Prostitution in Vietnam is illegal and a serious crime, although the government estimated that between 30,000 people in the country are prostitutes. Sex and the city wiki estimate puts the number between 20,000 and 25,000 individuals.
As a more conservative culture, the Vietnamese have less of a prostitution. Keep in mind Ho Chi Minh City is not a sex tourism destination, Thailand is a best choice for sex tourism. You may find many street hookers riding their bikes and cycles looking for people interested to have paid sex. Although prostitution is banned in Vietnam, it has not been eliminated completely. The locals refer to the prostitutes in Vietnam as butterflies of the night. They operate around certain places and streets in Ho Chi Minh City.
Warning: There is one big problem with the hotels in Vietnam, that is that technically speaking Vietnamese girls are not supposed to be in hotels with foreigners and some of the more traditional hotels will not let you in if you show up with a Vietnamese girl, especially late at night. Many guests have to check in to brand new hotels late at night because they had a girl with them. Make sure your hotel is on the same page as you before you pay. In Ho Chi Minh City, some of the prostitutes are into the sex work because of economic needs.
HCMC has some middle class escorts and mainly they are named call girls. Find phone numbers of call girls at different websites. Send SMS text message to a girl to ask for a date. If available, the girl will reply with a hotel name and address. Reply to tell what time you can come to the hotel. She will come promptly, have fun. You pay for the shot, not for the time, so no need to rush.
There are no real red-light districts in Ho Chi Minh City. The Hoa Binh Park in Ho Chi Minh City is one of the most talked about places in this matter. The place is located in the corner of Nguyen Chi Thanh Street and Hung Vuong. The place is situated in the border of two districts 5 and 10.