Black triangular object seen overtaking airplane during flight in Southeast AsiaThe sighting happened during a flight from Singapore to Kuching/Malaysia at approximately 3:30 PM.The plane (an Airbus A-320) already was at its full altitude of around 30000 feet for around 30-45 minutes going from west to east.When looking out of the window my girlfriend and I saw a rather small triangular shaped object flying from west-south-west to east-north-east, following a straight path and not changing its altitude.I estimated the object's size to be about 2 or 3 times the size of a Cessna-type airplane, its shape looked like a flat triangle and its colour was pitch-black without any reflections of the sun.It is difficult to guess the exact altitude but the object was crossing the upper parts and tops of cumulus clouds which our airliner was flying above, therefore its altitude might have been somewhere between 20000 and 25000 feet.The object’s speed was definitely faster than our airplane’s since in the end it overtook us and we lost sight of it when it entered an east-north-east located cloud bank ahead of our flight direction.I estimated the object’s speed to be at least 150%-175% of our airplane’s and it besides this it made no "phantastic movements" like sharp curves or such.It just constantly flew into one direction quite quickly.When I saw the object in the first place I thought it was another airliner, but when I realized its all-black colour having no light reflections at all, I had a closer look at it and figured out that its shape was very uncommon (it had no characteristics of an airplane) and its size was way smaller than the smallest airplane I know of being capable of flying in such an altitude.Unfortunately my photo and video equipment was inside my check-in luggage, so I could only observe it my eyes.I estimate the duration of the whole event to be about 1 or 2 minutes, from appearance of the object to losing it out of sight.