Where does “ชูวัช” come from?

ชูวัช (Thai) comes from English Chuvash, from Russian чува́ш — Chuvash (by ethnicity).

Ancestry of “ชูวัช”, step by step

Step	Language	Word	Meaning
1	English	Chuvash	From, or pertaining to, Chuvashia
2	Russian	чува́ш	Chuvash (by ethnicity)