Where does “พม่า” come from?

พม่า (Thai) comes from Burmese ဗမာ, from Burmese မြန်မာ — Myanmar; Burma; Burmese; Myanmar.

Ancestry of “พม่า”, step by step

Step	Language	Word	Meaning
1	Burmese	ဗမာ	—
2	Burmese	မြန်မာ	Myanmar; Burma; Burmese; Myanmar

พม่า — Etymology, Origin & Word History | Etymology Explorer