I passed my random drug test can I be tested again days later

Well, it depends. Who was testing you and why? Was this as part of a treatment program? Was it part of your probation or post-prison supervision? Part of a deferred adjudication program, like diversion? The answer to almost all (if not all) of these is likely 'yes.' If you are in a treatment program, they can ask you to take just about as many UA's as they want. You may still have avenues if it gets extreme in any of these situations, but, yes, you can be asked to take two UA's as part of almost any court program.

If your order of probation says that you are subject to random drug testing, then you can be tested again at any time. If there is any court order saying that you are subject to random drug tests, you can be tested at any time, and what is bad is that if you refuse, they take that as a positive result.

Yes. As the late great paleontologist Steven Jay Gould reminded us, randomness produces clumps.