Aria here, I'm on the Social Care team at Shopify. :)
Typically you'll find the sales tax is set up correctly in your Shopify admin, according to the business address you put on your store. You should find tax will only be charged to customers in Malaysia. Any International customers will not be charged tax. The rules do vary by country though and to be certain, I'd always recommend you ask advice from a tax expert local to you.
You can find more information on managing your tax settings in this guide.
Let me know if you need anything else. ?
Social Care Guru