@Siggi ******
No it isn't. A tourist visa is a tourist visa, a destination thailand visa is a destination thailand visa. They are different in every aspect of implementation and are treated differently (5 year driving licenses for example) in country. They have different working permissions and quite simply, nothing about them is the same.
As to visas being valid until expiry, that again is wrong when a visa has a grounds of issue. If they issue a tourist visa then you can always be a tourist, if they issue a work visa it is valid when you are still in work. That's how all the other classes work.
Enforcement is of course not consistent.