Yes, messboy is a vocation. The proper term is mess
steward, according to SAF 
. Messboys will be under QM side and their
direct superior/s will be the QM and RQ.
One of my poly classmate who OOCed from OCS was a messboy. Life was
quite good, obviously. If no officers were around, he would either
be polishing up on his billard/pool skills or he would be using msn
and playing diablo2 etc. He gets free unlimited access to the
normal beverages like milo,coffee and soft drinks. Once in a blue
moon, he might even be able to nick some tiger beer.
As for the downside, since he was the only messboy in the entire
officers' mess, he had to do the full shift, 7am - 7pm, (any
functions beyond that will be considered OT and he will get 1 day
OFF). He had to reach camp before 7am to get 4 loaves of bread,
kaya, butter etc from the cookhouse. He had to buy newspaper and
food for the officers sometimes. He also had to follow something
called "mess stewards directives and guidelines, a 5 pages worth of
typical SAF crapology. For some camps, they have 2 messboys and
their shift is divided into something like : 1st shift : 7am - 3pm,
2nd shift: 3pm to 11pm. For my friend who works alone, it was
indeed a bit üs« mei zhong bu zu.
On the whole, for kengsters and lazy bums, it will be the perfect
vocation. 
