Yes, PKM is internal Microst process which gets kicked up when Population of Full text index is going on.

SPIDStatusLoginHostNameBlkByDBNameCommandCPUTimeDiskIOLastBatchProgramNameSPID

58 RUNNABLE NT AUTHORITY\SYSTEMSERVERNAME . DBNAMESELECT 6320101/01 00:00:00PKM 58

59 RUNNABLE NT AUTHORITY\SYSTEMSERVERNAME . DBNAMESELECT 1253401/01 00:00:00PKM 59

61 RUNNABLE NT AUTHORITY\SYSTEMSERVERNAME . DBNAMESELECT 156901/01 00:00:00PKM 61