The difference between the single consonant is that double consonant are more stressed when pronounce. Just make a short paused before saying them to make the sound tensed.
ㄲ
pronounce as KK like 'Skip'
ㄸ
pronounce as DD like 'Stop'
ㅃ
pronounce as PP like 'spa'
ㅆ
pronounce as SS like 'sun'
ㅉ
pronounce as JJ like 'Pretzel'
BINABASA MO ANG
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RandomI'm not good in hangeul, but I did some research to help myself and you guys learn korean language.