I am going to try my hand at some fan fiction, are there any planets that are predominately Thai?
"Eight Nine Three" (Steve Mohan Jr.) references a character eating at a Thai restaurant on Altais.
In "Fortress of Lies," Chef Bellwood serves the Governor Thai Saumon Oriental in a sweet cream ginger sauce on Ningpo (albeit aboard a DropShip, so that's not necessarily an indicator that Thai cuisine is particularly good on Ningpo)
In "Irreplaceable," Hanse Davion takes a date to a Korean-Thai fusion restaurant on Addicks
Larsha (CC - near the Periphery border) is noted as having a Malaysian culture, but the Caballeros character "Sassy" Cassie, a Larsha native, has a mixed heritage that includes Thai.