Green’s Dictionary of Slang

soaped adj.

[soap n.3 ]

(S.Afr. drugs) under the influence of marijuana.

[SA]H.C. Bosman Cold Stone Jug (1981) II 30: ‘Blue’ was the most usual way of talking about being under the spell of dagga, but there were other expressions like [...] ‘herbed’ and ‘soaped’.