It saddens me to address this issue but I don't believe things will get better on their own. The nation's litter problem has improved in cities but elsewhere, Vietnam's garbage problem only seems to be getting worse.
My wife says litter and trash were discussed in class when she was a school girl in Da Nang 35 years ago! Over the years, I have witnessed some government efforts to address this matter through public information campaigns but it seems to have made little difference.
We were recently at a "resort" on Cat Ba Island and the trash on both sides of the road ran half a meter deep; even the otherwise beautiful beach sat addled with rubbish. We have a home in Hoi An and the road from the ocean in to the town is just awful with litter everywhere.
I saw a news feature on television last February about all the garbage in the water at Nha Trang. The report featured footage of tourists videotaping the trash float by. I'm sure they have never seen anything that bad before in their lives.
Given the way that the Vietnamese government is organized, the tools to solve this problem seem to be already at hand. Local Peoples' Committees have the means to organize folks to spend an odd day bagging this trash.
Perhaps the government ought to organize small-time criminals into "chain gangs" to be taken out, under armed supervision, to clean up this litter. Also, for minor offences or in lieu of monetary fines, the government may want to consider sentencing offenders to "community service" to perform work such as this.
I have loved your country and admired the Vietnamese people for their many good qualities for 45 years now, but this is one glaring issue that demands to be resolved.