Don't you think he has them on the roof as well? While not optimal, he will get some power no matter what direction he's facing, and that may be enough for the small task. Sri Lanka is ridiculously sunny.
He doesn't, and you replied without even watching the video. He has the usual tent on the roof, which would have been the best spot to mount the panels. Had the kid been some some western youtuber, those who downvoted me would be in line to write my same exact post. Please be honest with yourselves and others.
The rear side panels are hinged on top, so they can be raised to the sun while the tuk is stationary. As well, in the back, on the roof is clearly another panel.
You can see the lack of translucency at about 0:07, and his hand on the rear frame at 1:14. Actually you can see it a bit better at 0:04.
Further, its entirely possible that he has an extra vehicular set of panels at home base. He probably parks it with the doors open, facing the rising sun, catching some charge before the horizontal panels become directly illuminated.