Short answer: prove it with baby steps by requesting the opportunity to do a small-scale experiment telecommuting first. If you prove you can be effective from home, that’s a smaller ask of your employer and allows you to earn his/her confidence in a low-risk manner with little potential downside. Keep in mind this experiment is just as much for you as it is for him/her. If you’re not currently working remotely you need to prove this arrangement can be effective to yourself just as much.
If the experiment proves successful you’ll be in a stronger position with a small track record to then ask for the option to work from the road. Joining one of the travel programs like Remote Year, Wifi Tribe or We Roam will yield further confidence for your employer as there’s a “well-paved path” and a company providing some assurances like productive workspaces, reliable wifi, support staff, etc. Most programs also have an admissions team available to provide collateral, references and credibility to help win over your employer. Inquire about this with whichever programs you investigate and ask what support they can lend in helping you get buy-in from your employer.
I (luckily) had a very successful year while on Remote Year ultimately seeing a 70% increase on my yearly sales revenue vs. the previous year. Feel free to share this blog post or this talk I did at PressNomics both of which delve into the details of how the experience actually propelled my performance beyond what it was pre-nomadic working.