"I am not sure that the dropping of the final glottal stop with compensatory
lengthening in monosyllabic words is a standard feature of Siamese - I
suspect it is a dialect feature. Such words do not seem to derive from
Proto-Tai. Indeed, final glottal stops contrasting with other plosives do
not seem to be a very widespread feature in the Tai dialects. What do you
base your suggestions on? Apart from Siamese, I am only aware of them as
reflexes of final /k/." Richard WORDINGHAM, ENGLAND

Sorry, I didn't express myself properly.

I only meant that Siamese, like Tagalog, had the light glottal stop in the
initial position and the heavy glottal stop in the final position. The
compensatory lengthening of the vowel when the final heavy glottal stop is
dropped is peculiar to Tagalog. I don't know if this occurs in Siamese.