For the time being, I could not find any old example for this style. But the style 's currently used for machete size chopper (~20") around central Thailand.
I do not know the exact purpose of such inscription. My best guess is the inscription might be related to Korean war (we joined with the alliance in 1950). However, it 's only my guess
There 's a good indicator for its place of origin. During and short period after the WWII (1941-1957), Thailand 's Prime minister issued nationalism acts and using of some alphabets were prohinited. The inscription is "พ.ส." instead of "พ.ศ." or "ร.ศ." suggested that the blade was made in that period, in urban or sub-urban area (rural area was less affected by such act).