My grandfather has this story that he was in a cafe with a former British soldier involved in the Pacific theater and that the British officer was talking about being in Borneo during the early to mid part of the war. Halfway through his story, a german man stops him and tells him not only that he was there, but that the german troops were about to ambush the retreating british army. All of this happened in a cafe in Argentina which makes it a incredible coincidence. My question is, how possible is this? My grandfather gets forgetful on the details but there was some truth to this. That British soldier married into our family, his kids are my dads second cousins. Also my grandfather isn't senile or anything like that, this just happened in the 70s so I know it's a partially true story.
There was only one battalion of Indian troops on Borneo when the Japanese seized it. It's possible that your British officer was commanding troops in that battalion.
As to the rest of it? There's not a scrap of evidence for German land forces being in the Pacific at any time. German-Japanese military cooperation was extremely limited. The Germans operated some U-boats in the Indian ocean at times, and they sent some resources to the Japanese via U-Boat. But their army did not go east of Suez. They frankly had more than enough on their plates in Europe and had no reason to dispatch precious troops to a theater that neither needed nor wanted them.