From Irregular Regular: Recollections of Conflict Across the Globe (The Extraordinary Life of Colonel David Smiley Book 3, Sapere Books, 2020), Kindle pp. 153-154:
My briefing gave me the first indication of the extraordinary political set-up in Thailand. Technically, my briefing officer told me, Thailand was at war with the Allies, against whom she declared war when she was occupied by the Japanese. ‘Didn’t she fight against the Japanese when they invaded Thailand?’ I asked. ‘And why did she have to declare war on us?’ She only offered ‘token resistance’ against the Japanese, I was told, and declared war on us ‘under strong Japanese pressure’. She was, however, a most unwilling ally of the Japanese. ‘How do you know that?’ I said. One had only to look, he replied, at the size of the underground movement. It included not only a number of high-level politicians, service chiefs and government officials, but was led by the Regent himself. He went on: ‘You’ll hear a great deal of the Regent from now on. His real name and title is Luang Pradit Pridi Panomyong but he is known to all of us as “Ruth”, which is his codename.’
At the end of April 1944 the first British officer from Force 136 to visit Siam was Brigadier Jacques, codenamed ‘Hector’. He and Chin had been landed off the coast of Siam by Catalina flying boat and had then transferred to a fishing boat that took them to Bangkok. Hector had been a prominent lawyer in Bangkok before the war and had many friends and contacts there; he also spoke the language fluently. In Bangkok they had meetings with Ruth and some of Ruth’s friends, then returned the way they had come.
After Hector had reported to Mountbatten he returned to Bangkok by the same means, taking with him a radio and radio operator. He came out once more, when I met him, then stayed until the end of the war. As a soldier he insisted on wearing uniform, which caused Ruth a security problem. However, Ruth found him a safe house either in his own palace or the University of Moral and Political Science, where he was in daily communication with Force 136 HQ. As he was in close contact with Ruth, who had frequent meetings with the Japanese, he was able to pass on much vital information which would be on Mountbatten’s desk in Kandy within twenty-four hours. Hector remained the senior BLO [British Liaison Officer] throughout his time in Thailand.