BANGKOK — Massive occupations of two areas of central Bangkok the past two months show that the rise of Thailand's "red shirt" protesters is one of the most significant developments in Asia in 25 years, as it signals a new type of conflict involving entrenched elites and millions of workers who have migrated from farms to cities across Asia.

In the 1970s, when most Asians lived on farms, ideologues fought their battles in mountains and jungles across Southeast Asia. Now, after some of the largest demographic changes in history, radicals can recruit massive followings in cities such as Bangkok with millions of disaffected laborers who no longer have farms to return to.

When I first lived in Bangkok in 1987, the city of 6 million was dominated by Chinese-Thai business elites and Thai officials with fair skin and links to the monarchy. Farmers in Isaan in the northeast seemed to live in another century, plowing parched rice paddies with water buffaloes. Youth flocked to Bangkok for a flashier life.