The boundary for Myanmar appears to be wrong. I, apparently, have 2,000+ observations from that country, but I have never been there. ALL my observations have been from Thailand.
All I come across for Myanmar is a boundary box, which is very inaccurate.
By design all the borders are pretty “choppy” due to the impact on site performance it would have with highly accurate borders. Can you share a URL or screenshot where ~2000 of your observations are falling within Myanmar? I’m only able to find one (near the border on iNat):
Note that the search for Myanmar is done under Filters>More Filters>“Place”, not “Location”, which uses Google Maps instead of just searching iNat Places.
(Just a note – the rectangular bounding box effect I described above is sporadic. That’s the difference between the “Place” Myanmar and the “Location” Myanmar, while for example the Place and Location for Egypt are identical.)