Thai Airways International and Thai AirAsia suspended flights to Hong Kong after the Chinese territory closed its airport on Monday.
THAI announced the cancellation of two outbound flights, TG606 leaving at 4pm and TG602 departing at 6.30pm. A Bangkok-bound flight, TG 607, leaving Hong Kong at 8.45pm was also cancelled. Thai flights operate from Suvaranabhumi airport.
Thai AirAsia cancelled three flights, FD504 leaving Don Mueang airport at 3.28pm, FD502 leaving at 5.44pm and FD524 leaving Phuket at 4.02pm.
Their return flights, FD505, FD503 and FD525 from Hong Kong were also cancelled.
Hong Kong airport was swamped by protesters for a fourth day on Monday, forcing authorities to close it.
The Thai Consulate General in Hong Kong urged all Thais stranded by the protest at Terminal 1 of Hong Kong airport to "urgently leave" for other safe areas, including Terminal 2, Parking lots A and B, or Regal Airport.
It advised Thai passengers who already went through the immigration process to assemble at Gate 10.