Depends if he's proper African or from a "farang" country. In an everyday sense and usage "Negro", "Khon Africa" or "Khon Dam" - Khon meaning people and Dam meaning black, I've also heard Farang Dam and things like Negro America or Negro Angkrit (U.K.) for guys form the "west". Very often in a boxing context if the guy is from what would be deemed a "farang" country, they'd simply refer to him as Dutch for example, but always being under the umbrella of Nak Muay Farang because most foreign fighters tend to be white with a sprinkling of North Africans and only a few black guys. They have a rather large Nigerian community in BKK so are familiar in some regard to Africans, but also very wary as the Nigerian community is usually up to no good, like passport fraud, money laundering, fake dollar bills etc. etc. People from the Middle East, North Africa and South Asia are all termed as Kaerk even if they come form the States or the UK.
Danny Bill possibly the farang GOAT in terms of Thai Muay Thai was French Cameroonian and gets bags of respect in Thailand like Dekkers did. I've heard him called French, Cameroonian, as well as most of the above with the additon of also being Nak Muay Farang.
As like most things in Thailand the word farang can be bent to many usages, but on the whole is used in regard to white forigners where ever they come form. The word derives from colonial times when there were lots of French in neighbouring Cambodia and Laos, the Thai word for French is "Farangcais
". It also means Guava in Thai by the way and in Issan slang a white foreigner is "Backshida
" which also in Issan means Guava but on occasion is used in a negative way to talk about you behind your back rather than using the common word Farang.
The Thais are a very welcoming bunch but also super nationalists who routinely look down on elements of their own kind. They tend to view different ethnicity and nationalities threw very antiquated stereotypes and they tend to lump them all together, so if your white for example we all tend to like, eat and do the same things in thier eyes whether we're from London, Siberia or Helsinki. Kinda like westerners tend to do with Asians! "There all the same
" kinda thing.