Myself and my girlfriend were stood on our 27th floor balcony which faces north towards bangkok when we both saw a dull black triangle shaped craft approaching from the north at 1500ft away from us to the west travelling at a constant speed and horizontal flight. the craft had a dull dim orange colored rectangular panels in each corner 3 in total.It made no sound it had no usual aircraft id lighting it was totally silent no engine ir any sounds coming from it. we both clearly observed the craft for approximately 10 to 15 seconds it was not an aircraft in the normal sense. the craft flew north to south and we lost sight as it passed across in front of our building. we regularly see aircraft flying over us from bangkok airport so we are well aware of the charecteristics shapes take off and flight id lighting and flight paths of planes in this area this was not a plane.