1) All Xbox consoles have been region free since the Xbox One days (For games. Bluray / DVD movies still have region locks) .
2) You first need to have an Xbox account. You can create it from Xbox website, or from the Xbox console itself. Which country you create the account in, will also determine the currency you pay in. I created my Xbox account for the US. Once you have your Xbox account, you can subscribe to Gamepass for just USD1. 
3) Malaysia is not supported / listed. You will need to use an overseas address. A fake one will be just fine

The best way to subscribe though, is to convert Xbox Live Gold to Gamepass Ultimate. First, get an Xbox Live Gold subscription plan. Then, when you subscribe to Gamepass, it will convert your Xbox Live Gold subscription to Gamepass Ultimate. Example:

You buy 3 x 12 months of Xbox Live Gold. This gives you 36 months of Xbox Live Gold subscription. Then you upgrade your Xbox Live Gold subscription to Gamepass Ultimate for just USD1. This will convert the 36 months Xbox Live Gold to 36 months Gamepass Ultimate. It's cheaper than paying USD15 per month for Gamepass Ultimate. One thing to note though, this USD1 conversion only works once. After your subscription has ended, you can still do this conversion method, but it will be USD15 instead.

You don't really need a credit card to buy Xbox Live Gold in the first place. I just buy Xbox Live Gold gift cards. Just be careful that you buy the gift card for the same region that you registered your Xbox account. In my case, because my Xbox account is for the US, I also need to guy Xbox Live Gold gift cards for the US. There are other regions too, such as Singapore, Argentina, etc.