This is probably my own personal 'least interesting wader'. They are here in good numbers during winter. During hightide they roost in salt pans spending most of their time standing still or sleeping. I find it very hard to separate the birds when only one bird seen. Easiest is when several birds are closely together.
The Lesser seem to dominate in the pans whereas Greater dominate out on the sand spit. Apparantly Greater prefer small crabs to feed on (and there is plenty) but Lesser prefer smaller wormlike creatures found in the pans and the mudflats.
Here is a Lesser.
They often have a 'hunched' appearance.
Here with a Greater. Note the distinct difference in size, bill and posture.
Literature tells me that the race of Lesser found in Thailand: Charadrius mongolus schaeferi, has the longest bill of the Lesser Sand Plovers.
The nominate race of Greater found in Thailand has the shortest of the Greater races.
Greater in breeding plumage also has white in the otherwise black forehead. C.m. Schaeferi is all black.
Not too hard to tell them apart like this.