Japanese built submarines underway to Siam in 1938

A letter of the German naval attache in Japan dated Tokyo, Japan 30 June 1938 reported that the four Siamese submarines built by Mitsubishi, Kobe, Japan left on 4 June for Bangkok. Siam. The crews were trained in Japan in the past two years. Newspaper items suggested that the crew of the submarines numbered 210 men, something the German liaison officer doubted.

Source

High Command of the Kriegsmarine (OKM). Case 36