  For solid-state spin qubits, single-gate RF readout can help minimise the
number of gates required for scale-up to many qubits since the readout sensor
can integrate into the existing gates required to manipulate the qubits
(Veldhorst 2017, Pakkiam 2018). However, a key requirement for a scalable
quantum computer is that we must be capable of resolving the qubit state within
single-shot, that is, a single measurement (DiVincenzo 2000). Here we
demonstrate single-gate, single-shot readout of a singlet-triplet spin state in
silicon, with an average readout fidelity of $82.9\%$ at a $3.3~\text{kHz}$
measurement bandwidth. We use this technique to measure a triplet $T_-$ to
singlet $S_0$ relaxation time of $0.62~\text{ms}$ in precision donor quantum
dots in silicon. We also show that the use of RF readout does not impact the
maximum readout time at zero detuning limited by the $S_0$ to $T_-$ decay,
which remained at approximately $2~\text{ms}$. This establishes single-gate
sensing as a viable readout method for spin qubits.
