Don't quote me on this, but I believe the way to do that would be to add a custom interface field to your scene, then register the main Brightscript thread as an observer on the field. Then, in your event loop, you'd listen for an roSGNodeEvent that indicates that field has been updated, and trigger the playback. You'd likely want a second status field as well, so you can pass whether viewing the ad was successful or not back to the SceneGraph thread.
Seems very hacky, but I don't know of any other way to accomplish it with the current RAF library. Hopefully they're working on a native SceneGraph version.
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