Check if you’re able to apply for a six months multiple entries tourist visa. Even if you’re not allowed to do an extension this will potentially give you almost 3 x 60 days.
Tourist visa is not a guarantee anyway, but if you’ve just done one visa exemption entry before you went to Vietnam, you should be fine with another visa exemption anyway. Tourist visa might just be a bit more safe if you risk to get denied, and if you enter by land border with a tourist visa they’ll almost always let you in anyway.
A visa it’s not issued if your native language is English, but maybe more correct to say that the majority of the official English speaking countries are entitled to visa exemption.