Thai Airways International plans to decide on an order for new widebodies by the end of the year, and is likely to go with a mix of Boeing 787s and Airbus A350s.
The Star Alliance carrier could order up to 30 aircraft and hopes to finalise its decision by year-end, says a Thai senior executive.
"Boeing and Airbus have each made their marketing pitch, and it's now up to our team to assess the offers," he adds.
Thai is likely to order both the 787 and A350 but it is not clear if the order will be equally split between the two aircraft types.
"We need to be impartial to both," says the executive.
The new aircraft will help to replace Thai's ageing A300s, most of which will be retired in the next ten years.
Earlier this year, Thai said it aims to add at least 62 aircraft to its fleet over the next ten years as it phases out 57 aircraft.
Most of the new aircraft will be 300-350 seater jets, to be operated on both regional and intercontinental routes, it said.