Where does “รีกา” come from?

รีกา (Thai) comes from English Riga, from Italian riga, from Old High German riga, from Proto-Germanic rīgǭ, from Proto-Indo-European h₁reyk- — to scratch, cut.

Ancestry of “รีกา”, step by step

Step	Language	Word	Meaning
1	English	Riga	—
2	Italian	riga	line; stripe; parting
3	Old High German	riga	line
4	Proto-Germanic	rīgǭ	row, line
5	Proto-Indo-European	h₁reyk-	to scratch, cut

Every word from Proto-Indo-European h₁reyk- →Every word from Proto-Germanic rīgǭ →Every word from Old High German riga →