ㅅ / ㅆ are not pronounced as “s” when…
they are the last letters in a syllable
했
ㅅ/ㅆ ARE pronounced as “s” when…..
•they’re the last letter in a syllable & the first sound in the next syllable is a vowel
했어
if the following syllable starts with a consonant….
ㅅ/ㅆ get pronounced normally (d)
했다