Silent, dark chevron-shaped object flew over us and faded from view

My 8 year old son and I were out for a walk outside our apartment in District 2, Ho Chi Minh City, Vietnam. We stopped to look up at the stars in the clear night sky at about 7:30pm.
Suddenly my son pointed and exclaimed “Dad! Look at that!”
It took me a moment to make it out, but distinctly against the night sky there was a dark gray/navy “V” chevron shape to the south moving north towards us, pointy end leading. The leading tip of the chevron was an angle of about 45 degrees. It had sharp angles and shimmered around the edges, kind of like if I were looking at it through a hazy mirage. It trailed the shimmering for about half to full width of the object. It was hard to make out because it closely matched the color of the night sky, but it was just a bit darker. Totally silent.
My son claimed to see 5-6 dim orange-ish lights on the underside. I didn’t see any lights, although his eyes are sharper than mine. He also said he saw a cube-shaped object closely trailing the chevron, almost a part of it. I don't recall that, but I do recall there was a roiled air or vapor shimmering trailing the object closely, like a ripple. It may have contained another object shape close to the chevron or otherwise account for what my son reported.
We watched the object pass over us and across the Saigon river moving north. It moved in a straight line and uniform modest speed. It faded out on the other side of the river. I couldn't tell if the light angle changed such that we lost sight of it, or if it just faded and disappeared. About 30 seconds total viewing time.
I have no idea how far up it was because there was no reference point. My gut told me it was not close to the ground, up at least a few hundred meters and probably more. If that’s true it was massive. The wingspan (if you can call it that lol) was about the width of 3-4 fingers held together at arm's length. Much larger than I am accustomed to seeing jetliners.
Really no clue what this was, other than highly unlikely it can be explained by weather phenomena. I earned my private pilot's license and enjoy amateur sky-watching, so am familiar with aircraft. This was like nothing I've ever seen. The regular shape, sharp angles, uniform speed and direction suggested intelligent control -- by whom, I've no idea.