Thomburi started her career in 1933 as the Japanese "pocket battleship" Aki, while a world away the Nazi's similar Deutschland made headlines. Aki had the same triple 11" main armament built under license but poor manufacturing ruined their quality. At the time, the Washington Treaty was being scrupulously upheld by Japan and Aki's 'cruiser' tonnage was 2,500 tons over the 10,000 ton limit when completed. To save face and reduce tonnage two sets of boilers and all secondary armament were removed. The IJN wasn't pleased with the result so two 14" twin-gun turrets from the newly converted BBV Ise replaced the 11", and the ship was sold to Thailand as a capital ship to replace an old coast-defence ship of the same name. The IJN started a new, larger pocket battlecruiser (Chichibu) in secret, knowing that she would be too big for the Treaty definition of 'cruiser', but that Japan was going to abrogate the Treaty soon anyway.

Thomburi was gratefully accepted by Thailand and on the first day of hostilities successfully battled a demoralized French squadron off the Mekong. She regularly patrolled Indonesia and escorted convoys of raw materials to Japan. A raiding Anglo-American carrier fleet caught and sank both Thomburi and the convoy before land-based bombers and fighters of the 27th Air Flotilla drove the intruders off.