In Thai, you use the same word for grandchildren, nephews, and nieces. The base word is หลาน (lăan) meaning nephews, nieces, and grandchildren. But you can also specify the gender as I explain below.
![Grandchildren, nephews, nieces in Thai 1 Grandchildren nephews nieces in Thai](https://thaiwithgrace.com/wp-content/uploads/2020/07/grandchild-nephews-nieces-thai.jpg)
Grandson, nephew in Thai
In Thai to specify a male, you use ชาย (chaai). So grandson and nephew is หลานชาย (lăan chaai).
Granddaughter, Niece in Thai
In Thai to specify a girl, you use สาว (săao). So granddaughter and niece is หลานสาว (lăan săao).