Wong khrueang sai (Thai: วงเครื่องสาย, in Thai pronounced as /woŋ kʰrɯ̂əŋ sǎːj/, literally "string ensemble") is a musical ensemble in Thai classical music which consists primarily of string instruments. A typical khrueang sai ensemble features two two-string fiddles, one high and one low (saw duang and saw u), a three-string zither called jakhe, a vertical duct flute called khlui, hand drums, and various cymbals. Depending on the size of the ensemble, instruments may be doubled or left out. A three-string spike fiddle called saw sam sai may be added as well. The khim (hammered dulcimer) has become popular and is also used in this ensemble. In the 20th century, Western instruments such as the violin or organ have also occasionally been integrated into khrueang sai ensembles.
The khrueang sai is one of the quietest and most intimate ensembles in Thai classical music. It is used to accompany singing, dances, and holidays. It also used in impromptu occasions requiring music.
The following are some of the ensemble types, depending on the occasion:
Here is the definition of the khrueang sai according to the NIU South East Asia Studies department: