If I were you I would buy a new spark plug and keep it handy until the engine fail to start again. When it fails to start, I would remove the covers quickly, remove the spark plug wire from the engine's spark plug, and connect the spark plug wire to the new spark plug. Then I would ground the new spark plug to the tappet cover, and press the starter button to see if there is any spark at the new spark plug.
If you can't see any spark at the plug, it means that you are experiencing an electrical problem. Electrical problems can be caused by the CDI, ignition coil, plug wire, ignition switch, or faulty wire connections.
If you can't see a spark at the spark plug, first thing I would do is to try a new CDI to see if it makes a difference. The CDI's on Kymco scooters clearly do not last for ever. When the CDI's are dying, the results are exactly the same as your current experience.