The national carrier has been operating the flights to provide access to people who need to travel to the lower northern and upper central regions, which are difficult to access by road.
Initially the operation was scheduled to end this Sunday.
The special fights to and from Phitsanulok will also help transport donations and medical supplies from the Government's Flood Relief Operation Centre (FROC) and blood supplies through Thai Red Cross society to flood victims.
The airfare for one-way trip is at Bt1,250.
Flights operate using Boeing 737-400 aircraft with 149 seats. They depart from Suvarnabhumi Airport at 11.20am and arrive in Phitsanulok at 12.10pm. The return flight TG8707 departs from Phitsanulok at 12.50pm and arrives at Suvarnabhumi at 13.40pm.
For more information, call the THAI Contact Centre at (02) 356 1111 or log on to www.ThaiAirways.com