WDB FLT CREW RECEIVES FALSE EGPWS WARNING ON LOW FINAL APCH.

Narrative

WE WERE ESTABLISHED AND STABILIZED ON THE ILS TO RWY 19R INTO BANGKOK; THAILAND. THE WX CONDITIONS WERE CLR WITH VERY GOOD VISIBILITY. THERE WERE A FEW TSTMS ON THE HORIZON. APCHING 400-500 FT ABOVE THE GND; WE RECEIVED THE EGPWS TERRAIN WARNING 'TERRAIN AHEAD PULL UP.' I WAS THE PF AND CALLED FOR A GAR. WE EXECUTED THE MANEUVER AND ADVISED ATC OF THE GAR AND WHY. AFTER LEVELOFF WE DISCUSSED WHAT HAPPENED AND ALL 3 OF US COULDN'T COME UP WITH A REASON WHY THE WARNING ACTIVATED. WE ELECTED TO TRY THE APCH AGAIN AND DISCUSSED THAT IF WE RECEIVED THE WARNING AGAIN; AND WE WERE STABILIZED; AND COULD GUARANTEE SAFE TERRAIN CLRNC THAT WE CONTINUE TO A LNDG. ONCE ON THE ILS TO RWY 19R WE CONFIRMED OUR PATH AGAINST THE CHARTS AND ATC AND AGAIN AT 400-500 FT AGL THE WARNING CAME ON AGAIN. WE WERE ON THE PAPI AND GS AND I COULD SEE THAT THE TERRAIN WAS NOT A FACTOR; SO I CONTINUED FOR THE LNDG. WE LANDED SAFELY AND UPON BLOCK IN WE WROTE THE WARNING UP IN THE LOGBOOK AND FOUND OUT FROM MAINT THAT THERE WAS A PROB WITH THE EGPWS COMPUTER.