You may be best to check with all the major carriers but also what the rates might be in SouthEast Asia as they might actually have a better plan. It kind of depends where you will be staying for the majority of the time like will it be USA or SouthEast Asia? All carriers do offer roaming but it's usually an extra charge where you do this on an international basis. Like I know I can get local calling in USA and Canada but not elsewhere. That means I need to switch plans if going to another country. So you also need to check about that and ensure you can switch plans on a temporary basis if needed.