No, you must be present in Belgium to do the selection tests.
The written test is online so you just need a good internet connection.
For the oral test (part 1 – motivation interview): If you reside abroad, a Skype interview can be organised. For the other applicants, the test is organised at Enabel’s head office.
For part 2 of the oral test (assessment center): You must be present in Belgium. The test is organised at Enabel’s head office.