Correct, the US has stated repeatedly that its vaccine donations are made without conditions. It's a virtual certainty, though, that the set-aside for foreigners was brought up orally by the US side during preliminary discussions, but that they chose to omit it from any formal statements or agreements, presumably so that the Thai side can plausibly maintain a public facade that they are in complete control of the program. The idea that the Thai Government, of its own volition, decided in a spirit of kumbaya generosity to reserve doses for foreign residents is clearly laughable.