There is an answer above for Japan.
You won't be able to bring it into Australia. There are a few of the amphetamines available here for ADHD (dexamphetamine, Ritalin, etc.), but methamphetamine is not one of them. Further depending on the state there are legislative requirements that a tourist might not be able fulfill. (Don't quote me on that, but it is a pain in the neck and at the minimum you'd need to qualify for Medicare.)
I would suspect something similar applies for Thailand. Furthermore, Thailand is notorious for having extremely severe penalties for drug trafficking. (Although arguably the charge here would be a personal use charge, you wouldn't want to be the one who finds out that that "arguably" is wrong. Historically Thailand has hanged people for drug importation.)
The moral of the story is under absolutely no circumstance should your friend leave the country with methamphetamine. Leave it at home, and get doctor's advice on ADHD mitigations that are travel-friendly, or have a break. These medications are generally harmless to come off of. (Amphetamines do not have the physical withdrawal symptoms, and psychological withdrawal symptoms are usually a sign of a much more concerning underlying mental illness than ADHD, like abusive drug dependence.) As always, consult a doctor instead of the internet when it comes to your health.
Finally, I am not a lawyer, or a doctor, so any advice here should be taken with a pinch of foolish salt. Be skeptical, and ask experts IRL when it comes to stakes as high as this.