UFO Sighting in Bangkok, on September 1st 2015 – Short and strong storm cloud My wife took video and we saw object on playback.

My wife and I observed a strange and unusual storm from our condo balcony on 31st floor of our apartment in Bangkok. It was a very strong swirling storm that was low and passed over our condo. My wife decided to film it as it was unusual. On playback she pointed out the object shooting across the sky under the storm cloud. The object can be seen travelling from left side of picture at about 21 seconds into the video. She did not observe the object when she was actually filming. All I want is some kind of explanation as to what it could be as I am baffled. even if it is something normal, just knowing what the object is would be good.