BANGKOK, June 4 (Reuters) - Thailand plans to acquire

four Gripen JAS 39 fighter jets built by Sweden's SAAB

in the first procurement phase of its plan to replace

its ageing fleet of mainly U.S. aircraft, its air force said on

Wednesday.

Thailand has one of Southeast Asia's best-equipped air

forces, with 11 JAS 39 Gripen jets and dozens of American F-16

and F-5 aircraft, some of which have been in operation since the

late 1980s.

Last year, the air force announced plans to acquire more Swedish

jets as part of its long-term plan to buy 12 new fighter

aircraft.

The budget for the first phase is 19.5 billion baht ($595.97

million) and a contract for the four additional Gripen jets

would be signed in August, the air force said in a statement.

Thailand, which has a long history of military cooperation with

the United States and was designated a Major Non-NATO Ally by

Washington in 2023, had initially sought as many as eight

Lockheed Martin F-35 stealth jets, among the world's

most advanced fighter aircraft.

But the United States in 2023 declined to sell them over what

Bangkok said were issues with training, and technical

requirements including maintenance compatibility. The F-35 is

considered a sensitive export sold only to the United States'

closest allies, which in the Indo-Pacific includes Australia,

Japan, South Korea and Singapore.