This phrase is one of a list that I got one of my friends to recite for me, it basically means that somebody is all smiles on the outside but is miserable inside. Just because you want to use the phrase, however, is not a valid enough reason to suggest to someone that they’re fun-loving friend might need therapy, although I have met a lot of people to whom this phrase could be applied. The audio is below, along with a helpful explanation in Mandarin.
Quick note just to say that I use two different but similar dictionaries for this blog, a university one and the Ministry of Education one, but one of them keeps breaking down, the phonetic system used is the same on the whole, but there are some differences, for example “tshiò” here for 笑 is written “chhiò” in the other dictionary and similarly “tsāi” here for 在, can also be written “chāi”, though this is just two representations of the same sound.
I haven’t yet updated the google doc of differences between Taiwanese and Mandarin pronunciation for this post (an ongoing experiment), but check it out here and see if you observe any patterns.