In Cantonese writing 喇 (laa3) is one of the most common sentence-final particles - roughly the completive/softener 了+啦. In Mandarin the same character is also onomatopoeia for wind/rain (read lā).
mistakes
Don't confuse 喇 with 啦 or 了. In Mandarin texts 啦 is the usual softener; seeing 喇 at the end of a sentence strongly signals the writing is Cantonese.
Left-side mouth radical - pictograph of an open mouth, the indexing component. 喇 names sounds and instruments that come from a mouth-like opening: 喇叭 trumpet / horn, 喇嘛 lama. The same radical heads most onomatopoeia: 啊, 哦, 呢, 哈.
Right 剌 supplies the sound - là with a slight tone shift to lǎ / la. 剌 itself is 束 bound bundle plus 刂 knife, originally 'to cut against the grain.' Here only the sound matters - 喇 functions as a syllabic transliteration character in words like 喇嘛.
