This is the 3rd most frequent Thai word.
ม
The Thai word "ม" (pronounced "mo ma") is the 33rd consonant in the Thai alphabet and represents the "m" sound.
In this sentence, 'ม' is a shortened form of 'มา', the verb meaning 'come', used in the imperative mood.
มานี่สิ
Come here.
Here, 'ม' is part of 'ลืม', a verb meaning 'forget', showing its role as part of a compound verb.
อย่าลืมพบกันพรุ่งนี้นะ
Don't forget to meet tomorrow.
In this case, 'มม' is used as an example in context of explaining meaninglessness, showcasing 'ม' as a character in a context not typical of its word use.