Regex thousand separator multiple conditions

I can't seem to get by with a regex to remove thousand separators despite all my research and testing.

Indeed, either my regex does not work at all, or it does not work correctly (if then else conditions).

My final goal is to have a single regex to delete thousand separators, please find below examples :

 1.00 => 1.00 doesn't delete . because only 2 digits after it 
 1,00 => 1,00 doesn't delete , because only 2 digits after it 
 1.000 => 1000 delete . because 3 digits after it 
 1.000.000 => 1000000 delete . because 3 digits after it 
 1,000 => 1000 delete , because 3 digits after it 
 1,000,000 => 1000000 delete , because 3 digits after it 
 1.000,00 => 1000,00 delete . because 3 digits after it BUT doesn't delete , because . is found before
 1.000,000 => 1000,000 delete . because 3 digits after it BUT doesn't delete , because . is found before
 1,000.00 => 1000.00 delete , because 3 digits after it BUT doesn't delete . because , is found before
 1,000.000 => 1000.000 delete , because 3 digits after it BUT doesn't delete . because , is found before

I have to create a single regex because i work using a tool created by 3rd party on which i don't have the hand (.NET is used).

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