  Let $r,h\in\mathbb{N}$ with $r\geq 7$ and let $F(x,y)\in \mathbb{Z}[x ,y]$ be
a binary form such that
  \[
  F(x , y) =(\alpha x + \beta y)^r -(\gamma x + \delta y)^r,
  \] where $\alpha$, $\beta$, $\gamma$ and $\delta$ are algebraic constants
with $\alpha\delta-\beta\gamma \neq 0$. We establish upper bounds for the
number of primitive solutions to the Thue inequality $0<|F(x, y)| \leq h$,
improving an earlier result of Siegel and of Akhtari, Saradha & Sharma.
