Given a travel related situation, and given a specific question about the situation, summarize the question into a title

I am travelling to various destinations in Southeast Asia. What is the best way to go about getting cell + data service? Is there a telecom that offers cheap roaming throughout a broad region, or will I need to get a SIM card in each country I travel to (most of my destinations will be a few days at a time, the most being a week, so this would be a bit inefficient)?

Cellphone service in Southeast Asia?