Singapore Airlines also confirmed the death and said 18 were hospitalised, including a crew member.
Mr Kittikachorn said head injuries were sustained among seven who were critically injured.
At least 12 are being treated in hospitals, the airlines said, with the remaining passengers and crew receiving treatment, where necessary, at the airport.
"Singapore Airlines offers its deepest condolences to the family of the deceased," the airlines said in a statement.
"Our priority is to provide all possible assistance to all passengers and crew on board the aircraft."
After 11 hours of flying time from take-off in London, the aircraft sharply dropped from an altitude of around 11,300 metres to 9,500 metres within just five minutes as it finished crossing the Andaman Sea and neared Thailand, FlightRadar 24 data showed.
Dzafran Azmir, a 28-year-old student on board the flight, told the aircraft started "tilting up and there was shaking".
"So I started bracing for what was happening, and very suddenly there was a very dramatic drop," he said.
"So everyone seated and not wearing seatbelt was launched immediately into the ceiling."
"Some hit their heads on the baggage cabins overhead and dented it, they hit the places where lights and masks are and broke straight through it."
Uninjured passengers have disembarked and an another aircraft will fly them onwards, Suvarnabhumi airport said.
Singapore's Minister for Transport Chee Hong Tat said in a statement he was "deeply saddened to learn the incident" on flight SQ231.
"Ministry of transport, Singapore, Singapore ministry of foreign affairs, civil aviation authority of Singapore and Changi airport officials, as well as SIA staff, are providing support to the affected passengers and their families," he said.
"My deepest condolences to the family of the deceased."
Boeing said they were in contact with Singapore Airlines and stood ready to support it.
The last Singapore Airlines fatalities were in October 2000 when a plane crashed on a closed runway during take-off in Taiwan. Eighty-three died.
ABC/
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