Expat from the Latin "ex patria" fundamentally meaning not living in your birth or home nation. Nothing to do with percentages of anything. Ever.
Ergo snowbirds are expats, just the same as foreign workers in Thailand, retirees living in Thailand, those with Thai families and/or spouses, and digital nomads pitching their tents in Thailand are expats.
Two week millionaires, sponsors of sick buffalo owners, "resident tourists" (a dying breed), sexpats, mongers (more rare species) and others just passing through who complain about Thailand's archaic daytime alcohol bans, not so much.