I’ve been to both. Seeing your requirements I think Colombia would be the best fit for you since it’s close by, has lots of black people/Afro Latinos and isn’t that culturally different as compared to Thailand.
However, I enjoyed Thailand a lot more than Colombia for a few reasons: much more tourist attractions, More stunning than Colombia, more cheaper, good street food, better nightlife, more safer, more adventurous etc
I know nikkas just care abt ass here, but as a traveler, alot of these Latin American countries are really Americanized which really takes away the mystique. I went to Mexico and it was basically like a poor Texas.