Due to be signed shortly, the agreement solidifies a memorandum of understanding signed last June to establish Thai VietJet Air (TVJA).
It spearheads the intention of both sides to get Thailand's newest low-cost carrier (LCC) off the ground by about mid-year as it gears up to fulfil requirements including an airline permit.
"We're taking steps to start up Thai VietJet Air by mid-year,'' said Somphong Sooksanguan, president of Kannithi Aviation, part of the Kannithi conglomerate, whose core portfolio lies in debt-collecting firm Kannithi Co but also includes commuter airline Kan Air.
The proportion of TVJA ownership remains intact 51% by Kannithi Aviation and 49% by VietJet Air, which is backed by Sovico, a major diversified Vietnamese conglomerate with interests ranging from banking and manufacturing to aviation.
Mr Somphong insisted that preparations to launch TVJA have not been hampered by Thailand's civil unrest, which has cast a negative outlook on the airline sector.
TVJA is in the process of obtaining an air operator's certificate from Thailand's Civil Aviation Department while fulfilling other requirements.
A management team has been set up, with international aviation veteran Florian Preuss being appointed TVJA chief executive.
A team of 30 Thai cabin attendants are undergoing training, 10 Thai pilots have been recruited and office space and flight time slots at Suvarnabhumi airport have been secured.
TVJA has chosen to operate flights through Suvarnbhumi, discarding previous thoughts of service through Don Mueang airport.
"There is too much competition at Don Mueang, which is home to several major LCCs. It's better to avoid them by being at Suvarnabhumi,"' Mr Somphong told the Bangkok Post.
That decision means TVJA will consolidate the position of parent VietJet Air, which has been operating regular flights between Suvarnabhumi and Ho Chi Minh City and Hanoi since last year on Airbus 320-200 single-aisle jets.
TVJA will start with two aircraft of similar type for maiden flights to local cities and neighbouring countries.