36 thousands or 36 thousand?

Oh, The grand old Duke of York,
He had ten thousand men;
He marched them up to the top of the hill,
And he marched them down again.

You can have thousands of soldiers, but when you are being exact, you have n thousand of them. same for hundreds, dozens or millions.

To explain a bit: the word 'thousand' is part of the number, which is modifying the noun (whatever it is that you're counting). Because the number is greater than 1, the noun takes the plural form, but the number itself does not change form. Would you say "sixteens men" because sixteen is greater than one? I certainly hope not. "Sixteen thousand" is still a number, just like "sixteen" is; just because it's expressed in two words doesn't make you treat the individual words differently.

36 Thousand.

If it were some other noun, i.e. not just a number, then perhaps thousands would be appropriate — e.g. 36 pots of 'hundreds and thousands'.

But otherwise, thousand is the norm.

It's 36 thousand, because that is the naming convention in our number system. We do not say "two hundreds;" rather we say "two hundred."