Is the pilot doing the engine anti-ice check and bleed air heating/demisting check and getting the rise in T4 when they are tested ?
As haihio has stated - quickest way to see if you have a bleed problem - and no doubt you or pilot would have checked change in TOT from OFF/ON of each? If no change in TOT that would kind of indicate the issue?
Something I normally do on any ground run on any machine - cycles the systems that normally don't get used and in your case being in Malaysia neither probably do due to the climate, and it also dries out the plumbing.
The reverse applies in colder climates if you have AC - run it regularly otherwise the seals dry out and you lose the gas.