For Mandarin, I would say it’s The Moon Represents My Heart by Teresa Teng. She passed on, but this song lives on through her Boomer and Gen X fans, which is cascaded down to their Gen Y children and Gen Z grandchildren.
I’m not Thai, but I’m confident that every Thai person knows Loy Kratong because it is one of the best-loved festivals in Thailand.
Go on, introduce me to some culture. xP