@SoCal
You're right, a lot of people just type Mandarin and read Hokkien :-) "食饱未?" would be more accurate. Tsiah8 is the colloquial pronunciation (白读) of 食 (文读: sit8 or sek8). I am not sure about the 未 bue - maybe some people say 无 bo5, too?
Best,
Aurelio