騎

Phono-semantic compound (形聲 /形声, OC *ɡral, *ɡrals): semantic 馬 (“horse”) + phonetic 奇 (OC *kral, *ɡral) – to ride horseback

Wanderwort in the E/SE Asian Sprachbund. The STEDT reconstructs Proto-Sino-Tibetan *gi (“to ride; to sit astride; to sit (horse)”), and comments that "many of the TB forms seem to be borrowings from Chinese 騎".

Outside Sino-Tibetan, cognates are also found in Hmong-Mien, Tai-Kadai and some Mon-Khmer languages. Benedict (1975) surmises that this is an ancient loan into Proto-Sino-Tibetan from Austro-Tai:

... but these [Tibeto-Burman] forms appear to involve old loans from AT [Austro-Tai] with typical loss of an original medial *w (Thai *khwi ~ *gwi).

while Peiros (1998), Sagart (2006), Schuessler (2007) (who suggests that 騎 (OC gai, “to ride”) is possibly endopassive "let oneself be carried (on the back of an animal)" of 荷 (OC gâiʔ, “to carry”)) and Pittayaporn (2014) think the directionality of borrowing is reversed. The following excerpt is taken from Sagart's review (2006) of Matisoff's book Handbook of Proto-Tibeto-Burman (2003):

The collection of forms under Matisoff's high-vowelled *gyi 'ride' are from TB languages in contact with Chinese (Lolo-Burmese, Qiangic, Tujia): they are best regarded as late loans from Chinese. ... The idea that the Chinese vocabulary of agriculture, metallurgy, horse-riding etc. might contain numerous loans from an early SEA language is simply not to be taken seriously in view of modern Asian archaeology (Bellwood 1997), quite apart from the fact that it makes no linguistic sense (Sagart 1999 for metal names). Yet Matisoff's book is scattered with observations telling the reader that words like 'writing brush' and 'ride' just discussed may well be loans from Austro-Tai into ST (188; 504).

Below lists some cognates for "to ride" found in various languages in this Sprachbund.

* Lolo-Burmese: *gyi ~ dzyi: Burmese စီး (ci:), Nuosu ꋩ (zzy, “to ride; to bear (a rider)”), ꊪ (zy, “to cause to ride”)

* Southwestern Tai: *kʰwiːᴮ: Thai ขี่ (kìi), Lao ຂີ່ (khī), Zhuang gwih

* Hmong-Mien: *ɟej: White Hmong caij

* Mon-Khmer: West Bahnaric *ɟih, Khmer ជិះ (cih), Vietnamese cưỡi

Also compare Proto-Austronesian *sakay (“catch a ride, join a group, ride on something”).

Pronunciation 2 is a Late Old Chinese general purpose derivation from Pronunciation 1 (Schuessler, 2007).