may be it is just a lazy sound, but it is more commonly used than the standard sui3 sound.
It’s simply a tone change, not a lazy sound.
For a Cantonese compound noun or ‘V + N’ structure, the non-essential last syllable is often taken out for the sake of brevity, thus resulting in a change to Tone 2 in the resultant last syllable.
For example: (1) compound noun - 西芹菜 sai kan4 coi → 西芹 sai kan4*2; 土地公 tou dei6 gung → 土地 tou dei6*2; 豆沙月餅 dau saa jyut6 beng → 豆沙月 dau saa jyut6*2.
(2) ‘V + N’ structure - 講故事 gong gu3 si → 講故 gong gu3*2 (similarly 講笑話 gong siu3 waa → 講笑 gong siu2); 炒魷魚 caau jau4 jyu → 炒魷 caau jau4*2; 夠皮費 gau pei4 fai → 夠皮 gau pei4*2.
I am not suggesting the 'sui2' prounouce be included in 笑 character page, but I think for the phrase 講笑, the 'sui2' pronunciation should be added.
A note on the change to Tone 2 can be found in the 講笑搵第樣 entry.
And you are right: we can’t include tone 2 to all those character pages because too many nouns (and verbs) could be affected by such tone change.
It’s simply a tone change, not a lazy sound.
For a Cantonese compound noun or ‘V + N’ structure, the non-essential last syllable is often taken out for the sake of brevity, thus resulting in a change to Tone 2 in the resultant last syllable.
For example: (1) compound noun - 西芹菜 sai kan4 coi → 西芹 sai kan4*2; 土地公 tou dei6 gung → 土地 tou dei6*2; 豆沙月餅 dau saa jyut6 beng → 豆沙月 dau saa jyut6*2.
(2) ‘V + N’ structure - 講故事 gong gu3 si → 講故 gong gu3*2 (similarly 講笑話 gong siu3 waa → 講笑 gong siu2); 炒魷魚 caau jau4 jyu → 炒魷 caau jau4*2; 夠皮費 gau pei4 fai → 夠皮 gau pei4*2.
I am not suggesting the 'sui2' prounouce be included in 笑 character page, but I think for the phrase 講笑, the 'sui2' pronunciation should be added.
A note on the change to Tone 2 can be found in the 講笑搵第樣 entry.
And you are right: we can’t include tone 2 to all those character pages because too many nouns (and verbs) could be affected by such tone change.