  Fast radio busts (FRBs) can exhibit a wide variety of polarisation
properties, not only between sources but also from burst to burst for a same
one. In this work, we revisit the polarisation characters of coherent curvature
radiation from a bulk of charged bunches in the magnetosphere of a highly
magnetized neutron star. FRBs have been observed to have a variety of
polarisation features, such as high levels of circular polarisation or a sign
change of circular polarisation. High linear polarisation would appear when the
line of sight is inside the emission beam (the on-beam geometry), whereas high
circular polarisation would be present when it is outside (the off-beam
geometry). By considering two scenarios of the ``bulk shapes'' (thick vs.
thin), we apply the model to explain the polarisation features of three
repeating FRBs (FRB 20201124A, FRB 20190520B and FRB 20121102A). Most bursts
are dominated by linear polarisation and negligible events have sign changes in
circular polarisation, suggesting that such FRBs are most likely to be emitted
by the ``thin'' bulks with large opening angles. The higher probability of
``thin'' bulks could be meaningful for understanding repeating FRB central
engine, i.e., the sparking dynamics to produce different bulks of energetic
bunches on a neutron star surface.
