A shocking truth.

[Ming-Yan]

Suicidal thoughts are not true colours and confronting it in that manner will not help. Just try to convince your brother how much he means to YOU and what it would be like if he wasn't around/all the stuff he could miss out on. You need to make him believe there is value to life.

When I was in a bad state I would write many times in notes that it wouldn't matter if I lived or not...I eventually ended up trying to get over it on my own by setting a goal. That goal is quite obvious and I have stated it many times, but I still know that if I accept the fact that what I am trying, is impossible I would probably be depressed again.

Sam needs something he can strive for in life so he no longer thinks suicide is the answer. It might have been covered up, but it ALWAYS is people don't want to share feelings like this and people that do are usually posers. It wasn't a blanket of lies...it was an attempt to isolate those feelings.
The only problem is although he may not want you to know, you not knowing is worse over all.

TL;DR Talk to him and make him have fun.