Look up what the name Pakistan is derived from (HINT: It's an acronym) and its history.
India has 1.37 billion people
780 languages (2nd only to New Guinea)
250 languages almost in addition to those that have died out in the last 50 years or so.
86 scripts.
7 major religions (and a plethora of minor ones).
Caucasions, Dravidians, Mongoloids, with some Melanesian admixture in the South.
Mind you, these people go back thousands (as in HUNDREDS of thousands in some cases) of years with multiple cultures coexisting. None of this recent colonization and immigration going back a mere five centuries with everyone adopting one single bland culture dependent on appropriating others into its own for growth and vitality.
You will also some similar diversity and blending albiet on a smaller scale (being that it's a smaller area) leaning to a majority Mongoloid (Malay mostly) population in Thailand.
China also is multi racial, ethnic, linguistic, religious, etc. In four THOUSAND years as a country, a few nations have gotten taken over, and some other folks have dropped by as well (they even have their own Jewish population which some assert to be one of the lost tribes of Israel, as does India as well). Its western Province of Uighurstan is a blend of Caucasion and Mongoloid going back to its days as part of the Iranian Empire, the Mongol Invasion, and the Silk Road, etc. You can literally see various blends side by side like it's no big deal because it isn't to them.
If you want to see diversity in Saudi Arabia, just look at the mutli racial Royal Family.
Saudi Arabia actually picks up by boat and delivers tons of people from Africa, India, and as far as the Phillipines for cheap labor in anything from oil rigs to nannies.
They don't need diveristy? They've had for over two MILLION years when ancestral humans first walked in Asia.
History does go back farther than 1776. Learn some.
Caption this Meme 