All unlocked iPhones can now be used anywhere in the world, regardless of supported bands. However, in most cases you can't submit them for warranty claim at Malaysian AASPs.

In Japan, the only way to get unlocked iPhones is to buy full price at official Apple Retail Store. Malaysian AASPs also won't support warranty claim, and you can't turn off the camera sound.

Hong Kong iPhones are usually unlocked. Can be used here, but not supported by local AASPs.

US iPhones are unlocked if purchased at full price at official Apple Retail Stores. All models wil work here, but only AT&T or T-Mobile models will be supported by local AASPs for warranty claims.

malaysia do not have OFFICIAL Apple Care Center except Machine's Authorized Service Center...
do not confuse yourself... Machine service sucks... i complaint to Apple care online only can get my replacement...
your phone or ipad drop before got small dent on the corners can't claim warranty...
although without cracks on screen and only button problem or the device hardware problem...
work thru the hard way about 1 week+ later only i manage to get back my device...