Maybe. You don't given any details of your planet re: how thin the atmosphere really is, and what is the required escape velocity (or the details that would allow its calculation).
Ejecta velocities, magma chamber pressure and kinetic energy associated with the 1968 eruption of Arenal Volcano suggest the eruption velocities could reach as much as 2 km/sec. This would be sufficient to achieve lunar orbit. If the moon has significant air drag, orbit would not be possible though.
You want high vulcanism, but presumably not enough to destroy to the planet. Yet you also need a low escape velocity and no (if possible) or very thin atmosphere.
Put your planet in near orbit of a gas giant to cause lots of tidal heating in the core, or you could just have a lot of uranium and thorium in the core compared to Earth. If you need a breathable atmosphere but thin as possible, make the atmosphere essentially pure oxygen with a trace of CO2 at about 0.2 atmosphere of pressure (your planet will be a little oxygen deficient compared to Earth, but quite breathable).
Now, make your vulcanism primarily due to an extremely powerful and very tall volcano or chain to get the "launch point" above most of the atmosphere. Due to the lower gravity, you may be able to make the volcano 30 km high, maybe even a little more. Granite flows downhill under sufficient pressure given time, so there is a limit to how tall a mountain can be.
At this point you can make the orbital volcano ejecta believable if not entirely realistic. Keeping a breathable atmosphere might be hard to explain - perhaps oxygen was unusually abundant originally and it is still seeping out from the interior. Still needs to be larger than the moon to keep an atmosphere, probably Mars size would be needed in addition to the ongoing replacement of oxygen.
When I read your question, I thought you were interested in a thick orbital cloud. Now I think you are talking about an atmospheric cloud.
Re: Having a thick volcanic clouds within the atmosphere it is not necessary at all. Large volcanic plume have been seen on Earth up to 50 miles above the surface. This is primarily a result of the warm air rising. To keep a consistent cloud, the vulcanism would have to be ongoing. Historical heavy eruptions on Earth only generate a cloud dense enough to obscure for a fairly short duration (weeks or months) and never world-wide. Even a super-volcano such as Yellowstone is not expected to cloud over the whole planet.
To keep cloud duration high you actually are better off with a thick atmosphere, which is very hard to justify on a small planet, and it makes orbital insertion impossible.
A possible solution to keeping a dark sky that is a result of vulcanism is to add biology into the mix. Say that these is a common bacteria adapted to using the volcanic material in the atmosphere. The bacteria consume this and eliminates the waste as microscopic particles of soot. This type of soot could remain in the atmosphere for many years if no rain, etc. washes it out. A number of earth bacteria are sulfur based, it is not inconceivable that a bacteria could consume sulphur and CO2 and end up expelling tiny soot particles.
Alternatively, you could have a high carbon planet, and carbon or hydrocarbons are a large component of the hot volcanic exhaust. If these burn incompletely you get soot. These soot particle will not generally be small enough to stay in the atmosphere for years, so this would be considerable less effective in generating permanent dark clouds.
Since you don't need a breathable atmosphere at all, and you apparently want the cloud to be orbital, you don't want any atmosphere at all. Any atmosphere will cause drag in low orbit, so get rid of the atmosphere.
Forgot to mention you want to give your planet a fast spin to that the ejecta has a relatively large angular momentum. Only a small fraction of the ejecta will be able to stay in orbit (as a result of secondary collisions) and it will tend to stay in concentrated in a band with a latitude roughly less than or equal to the latitude of the volcano. You minimum the orbital band thickness (along the north/south line) by placing your volcano near the equator. The natural tendency of the orbital rubble will be to form a ring, not a cloud. As the rubble interacts, it will naturally become of very thin orbital ring. This takes some time, and since your ejecta in continually renewing the ring, you could have essentially a ring with some thickness. There is no believable way to cover the whole planet, or even a large fraction of the planet.
Since you don't need atmosphere, making the planet smaller will reduce the necessary orbital velocity too. However, this will also tend to reduce vulcanism, so you need even more uranium/thorium or tidal stress to generate vulcanism.
Again, I am arguing that this answer is only plausible, not realistic. Your need to use as many of the circumstances I've mentioned to maximum the density of the orbital cloud and believability.