There is a sense of "pre-mourning" in this sentiment. By stating that they will leave "not long from now," the speaker acknowledges an inevitable end, shifting the focus to the value of the present moment.
In a social context, it is a gentle way to signal a departure without being abrupt, maintaining the Thai cultural value of kreng jai (consideration for others' feelings). eek mei naan chan ja pai
To provide a more tailored review, are you looking for an analysis of a with these lyrics, or do you want to explore the cultural context of this phrase further? Useful Thai Phrases - latranslation There is a sense of "pre-mourning" in this sentiment