Well, for one, that's Phuket Word in the screenshots, and he can't get anything right to save his life, so I'd consider it debunked right there.
Joking aside, we'd need more specifics on exactly what the claim in question is. Based on the screenshots, it looks like he's commenting on the "Eratosthenes experiment", which uses the lengths of shadows cast by sunlit objects to determine the shape of the Earth. If that's what it is, I'd consider Sly Sparkane's experiment on the subject to more or less be the definitive test. Very carefully gathered data, well presented, with a virtually inescapable conclusion.
Sly Sparkane - Flat Earth: Debunked
He first maps the shadow angles to their locations on an AE flat map. The result is shown below:
If the situation is a small sun circling above a flat earth, all the lines should point directly at the sun, allowing it's altitude to be triangulated. This is quite clearly not the case, so the option is ruled out. Secondly, Sly mapped the data onto a sphere of 3959 miles radius, yielding this:
If the sun is very large (e.g., larger than Earth) and very distant, the incoming light rays should be effectively parallel. My brain is too tired to create the appropriate syllogisms, but the flat earth model w/ close sun doesn't accurately predict the observations, while a spherical earth of 3959 miles radius and a distant sun does accurately predict the observations.