In the U.S., drug testing has been a major part of internal and external corporate safety programs since the mid 80's and more recently, part of federally mandated requirements for all Air Carriers and Repair Stations performing work on Air Carrier products.
For the Part 135 Operators, certified programmes for Drug, and more recently, alcohol, testing are a mandatory provision for the issuance and continuation of an Operators Certificate.
This system is administered by the DOT, rather than the FAA, and in my experience is managed the way the Nazi's would run it, (although they are not allowed to shoot you!)
Prior to federally mandated drug testing, however, many companies initiated their own Drug Test policies as a means of getting a significant break on Workers Compensation Insurance rates. These testing programmes became integral with Company safety programmes, many since the mid 80's.
In addition to internal safety programmes, many customers will require that all contractor employees be tested under their programme, prior to participating in larger projects. As with any Corporate policy(?), there must be a defined protocol for the administration of the testing process.
The testing process may be based upon many requirements, eg;
Pre-Hire, Random, Just Cause,lost-time accident, return to work, etc.
In the U.S., there are many requirements and procedures to ensure that the legal rights of the individual are not compromised. I would think that Esso has a similar policy, although subject to Malaysian interpretation.
All Drug testing here;
advises the subject, which drugs they are being screened for.
provides for the listing of any prescription, or non-prescription drugs which are being taken.
maintains the anonymity of the test subject,
The only Aviation guy I have ever had fail a drug test, failed for Opiates! As I have known him since he was a kid, I was extremely surprised, but the company would not hire him. He told me that he had never, ever, used drugs and was totally unable to comprehend how they could be detected within his system. However, he recalled that on the first day at work, he had brought dough-nuts and muffins in for everyone in the hangar and had eaten a Poppy Seed muffin causing the test outcome.
I was able to convince the company to retest him and he passed, but I found that whole process rather worrying.
I would recommend that you closely review the policy of Esso Malaysia, focusing on the testing, prescription drug, appeal and medical oversight process.
Examine the copy of the test paperwork given to the employee, for the provision to report prescription, or other drugs that were being taken at the time of testing.
If the testing detected prescription drugs, properly prescribed for the individual, it may well be worth your time to ask the prescibing doctor to contact the Esso employee (Doctor?) responsible for overseeing the programme, to ensure that accurate information is relayed.
If you have a sound argument, put it all on paper, copy it to your local management as well as the H.R. director of your employer, plus all the involved Esso management.
The purpose of drug testing is to eliminate impaired employees from the workplace in the interests of Safety. There is no benefit in penalizing the innocent, but be aware that the appeal process, if not fought with complete honesty may do irrepairable damage to the integrity, and career of the individual involved.
I think I have been drug tested 6 times in the last 18 months!