Under what conditions will permanent residency get revoked by the govt?

Something along the lines of leaving the country under some type of scenario?

If you leave without a re-entry permit to use when you enter the country PR will be lost. Being out of the country for more than a year also makes it invalid.

See Section 7 and Chapter 5 (Section 40 to 52) of the Immigration Act: http://www.immigration.go.th/nov2004/en/doc/Immigration_Act.pdf

Also the gov can revoke PR if one is deemed a national threat, committed certain crimes etc