The government of Thailand constitutes its new national air carrier at Bangkok on March 1, 1947. The company is equipped with one of the former Aerial Transport Company of Siam, Ltd. (ATCS) Fairchild Model 24Js that had survived World War II, together with 4 Douglas DC-3s, 2 Beech 18s, and 6 Consolidated L-5s. Revenue services commence on March 3 from the capital to Chiangmai and Chiang Rai. The remainder of the old ATCS routes are restarted during the remainder of the month and into April and May.
SAC inaugurates regional services on December 22 with a route from Songkhla to the Malayan city of Penang. International expansion continues early in the new year. On January 16, 1948, a DC-3 service is launched to Phnom Penh and Saigon, followed by Hong Kong three days later.
To handle this service increase, the fleet grows on January 23 through the addition of five Beech C-35 Bonanzas. This first quarter burst of development sustains the company through the remainder of the year.
Two final markets are added in 1949 as SAC starts flying to Calcutta via Rangoon. The last aircraft to join the fleet are six Noorduyn Norseman in 1950.
The new decade begins with a number of accidents.
A DC-3 with 5 crew and 11 passengers strikes high ground at Cape d’Arguilar, east of Hong Kong, on April 9, 1951; there are no survivors.
A C-54B must be written off after a bad landing at Bangkok on July 13; there are no fatalities.
A DC-3 with three crew aboard overshoots the runway at Bah Fai, Thailand, on August 20 and crashes; although the aircraft must be written off, there are no fatalities.
Despite these losses, further significant company development is anticipated. To that end, the airline purchases Pacific Overseas Airlines (Siam), Ltd. on November 1, 1951 and the same day, the two concerns are merged to create Thai Airways Company, Ltd.