Tonguez
A suffusion of yellow
It was 3e era, short little optional Oriental Adventures add-on. IIRC, the official content was only about 10 pages or so, but it was the only time I can recall that they tried to flesh out the idea of playing in something that had flavors of South Asia (specifically the Indian subcontinent) instead of the usual Ninja / Kung Fu "fusion" they serve up as a "pan-Asian" campaign setting.
It was more useful to get you started on your own homebrew than as a real campaign setting, TBH. I'd love to see them revisit it!
Agreed and Mahasarpa is still available for download too.
And although the ‘Hindu‘ themes give the impression of it being ‘India’ focussed, James Wyatt said his campaign was inspired by Angkor Watt (Cambodia) and I played a game set in Vietnam.