I guess it is fluffy as usual - I read this excerpt from the Bangkok Post today slightly differently :

Those who are healthy can discard the mask when alone, exercising, eating, drinking or in an open space where social distancing can be practised, the DDC said.

I guess the ‘open space where social distancing…’ part is up for interpretation, in which case I guess you are right.

I have the same experiences as you regarding mask wearing in offices - and it has been this way for months now, as people pretty much stopped bothering. So whenever there is a ‘silent consensus’ (secret hand-shake or bat-signal ) that everybody is fine, people take off their masks.