I wish I could comment on this topic but I don't really know much about the way the Vietnamese had treated Hun Sen while he stayed in the VN prison.I've heard that they gave him allowances! He tried communicating with the guard in French first before he learned Vietnamese language.He really hated Pol Pot the mad man, so he found some comfort there. He probably was not the only Khmer prisoner there. Later on the Chief of the prison guard became his friend. So of course the bonding was made since then.