The classes K1 and K2 refer to a total of eleven Pacifics of the Federated Malay States Railways, which were built in 1927 and 1929. They were basically an improved version of the class L which had been delivered by Kitson in 1921. In 1927, Beyer, Peacock & Co. delivered seven and two years later Robert Stephenson & Co. delivered four more.
Robert Stephenson variant
flickr/Historical Railway Images 
Since the letter K had been occupied by a single other locomotive until recently, the class was initially called “New K”. Later the two series became K1 and K2. During the Second World War, six were probably brought to Siam by the occupiers. The remaining Beyer locomotives were decommissioned in 1958 and 1959, the Stephenson ones only in the 1970s with the end of steam traction in Malaysia.