Books in the Operation Janus series

In post-WWII Laos, Vietnamese communists secretly commence to infiltrate the kingdom. They are countered by four dedicated Lao 'moles' who try to thwart these aims. Gurkha Colonel Jason Rance is unwittingly dragged into a confrontation between one of the Lao moles and a Thai spy and the mole gives him a ring as a reward for saving his life. During his appointment in Laos as military attaché, Rance becomes a target of the KGB and of the Vietnamese communists, and is sought by the remaining three Lao moles because of the ring in his possession.