So far, the availability of internet in Southeast Asia has been surprisingly extensive. It’s not always the fastest which, depending on the type of work you’re doing, may be an issue. But it gets the job done for me and for the most part I’ve been really happy with the coverage.
That said, if I was spending longer time in transit, or venturing out to really remote areas, I’d probably get some sort of data plan for my computer. They’re really cheap out here so if even if you do need one it shouldn’t be an issue.
But as it is now, about 90% of the places I’ve stayed have had some kind of wifi, and even when they don’t there’s sure to be a cafe or restaurant nearby that does.