This is almost certainly not true.
Let's start with basic information, the self-identities ethnicity of NASA employees. Fortunately this was measured for us as part of a diversity survey. Here are the 2015 results.
The graph of ethnicity is a few screens down and shows that around 7% are of Asian ethnicity (what a native Sri Lankan would count as). Clearly this debunks both the Sri Lankan and Indian claims. Note that the claim of Sri Lankan or Indian nationality is narrower than the ethnicity measure. Someone born in the US to one or even two Sri Lankan or Indian parents might claim Asian ethnicity but probably not that nationality.
There is a small possibility of discrepancy in that the survey is of all NASA employees, which would include non-scientists. NASA employees around 18,000 people, not the 2,400 claimed. It is theoretically possible that Sri Lankans or Indians are massively overrepresented in the scientist group. It would however be extremely implausible.