What statistics are you looking for, bombing in North Vietnam or bombing in South Vietnam? The Socialist Republic of Vietnam (the DRV after 1976) won't have info on South Vietnam. In any case, depending on the information you are seeking, the data might be better and easier to obtain from US official sources, since they were dropping the bombs.

[The other issue to keep in mind is that history in the SRV is incredibly politicized. You have to be very careful when dealing with their histories and data. Since the party dominates the state, history must be written in a way that re-affirms the legitimacy of the party, not necessarily the truth.] I can recommend others, but this is one of the main historical publications in Vietnam, and has been translated into English:

Victory in Vietnam: The Official History of the People’s Army of Vietnam, 1954–1975 by the Military History Institute of Vietnam, translated by Merle L. Pribbenow (University Press of Kansas, 2002).