Filipino Boyfriend Uses Shabu "casually"

So recently I have learned that my boyfriend uses shabu with his roommate and friends. I started thinking he was using months ago but didn't have any proof. He claims he uses it casually and only uses it to stay awake but I feel as if he does it more then casually. I'm not allowed in his room where him and his roommate share even to borrow a towel or something along those lines. He has an addictive personally as he smokes already and gets addicted to video games and certain activities very easily. We haven't had a conversation about the usage yet because I'm so angry that I feel as if we talk about it I will just end up yelling at him and I don't want that. He says it's normal in his country (the Philippines) but I as a Canadian find this disgusting. I guess my main question is do you think it is possible to use this substance casually and what do you think I should do. Also what are some ways I can tell he is still using if he promises to stop I want to be able to tell if he is lying.

Ps. He smokes it rolled in paper towel and I think sometimes with tinfoil how ever that would be done. When he does it he will disappear into his room for like 10 minutes. He seems to be able to hide the fact that he's used because I don't see too major of a difference in his behaviour yet. Sometimes he twitches and grinds his teeth in his sleep but that might be because of something else. And only once or twice has he actually stayed up the whole night. He eats normally but I think recently he has been doing it more often because he's lost weight in the last couple months without upping any activity or changing his diet.

Sorry for how all over the place this message is I just found out two days ago and I'm very angry, sad and filled with anxiety all at the same time.
To enraged girlfriend, my boyfriend and I have broken up for 2months now due to his meth use. We've been on long distance relationship for 5years. 2years ago, I found out about his addiction. He promised me he will never do it again, even had a tattoo as a constant reminder of his 'dark time' so I believed him. Until, I found out he had recently been using again. Constant worries, fights, arguments was just not enough for the both of us. So I've decided to take him abroad with me to find a job. Meth is no way to be found in the country where I work. So one day while I left him for work at my apartment, he was gone. I went home to an empty house. He went back to our home country, I pressume he is happy with his friends and especially with his meth. He was the 'love of my life' and sad to say, I lost the 'love of my life' over meth. I've never spoken to him again, changed my number, deleted social media accounts and to be honest, it still hurts so bad. RUN! As far away as you can! There is just nothing we could do for us to stop them until they decide to end it themselves. Believe me, the casual and occasional use will definitely lead to habitual using. For me, waking up to a new day is better than yesterday. But God knows how much I miss him and love him. I pray everyday he'd stop using and do good in life. As for me, I just need to accept that sometimes, things are just out of our hands. Best of luck!