  We calculate the mass spectrum of the $Qs\bar q \bar q$ $(Q=c, b)$ tetraquark
states with $J^P=(0,1,2)^+$ using the AL1 quark potential model, which
successfully describes the conventional hadron spectrum. We employ the Gaussian
expansion method to solve the four-body Schr\"odinger equation, and use the
complex scaling method to identify the resonances. With the notation $T_{Q s,
I(J)}^{\text {Theo. }}(M)$, we find several near-threshold bound states and
resonances, including $T_{cs,0(0)}^{\mathrm{Theo.}}(2350)$,
$T_{cs,0(0)}^{\mathrm{Theo.}}(2906)$, $T_{bs,0(0)}^{\mathrm{Theo.}}(5781)$,
$T_{bs,0(1)}^{\mathrm{Theo.}}(5840)$, and $T_{bs,0(0)}^{\mathrm{Theo.}}(6240)$
which are close to the $D\bar{K}$, $D^*\bar{K}^*$, $\bar{B}\bar{K}$,
$\bar{B}^*\bar{K}$ and $\bar{B}^*\bar{K}^*$ thresholds, respectively.
Furthermore, their spatial structures clearly support their molecular natures.
The resonance $T_{cs,0(0)}^{\mathrm{Theo.}}(2906)$ has a mass of $2906$ MeV, a
width of $20$ MeV, and quantum numbers $I(J^P)=0(0^+)$, which may serve as a
good candidate for the experimental $T_{cs0}(2900)$ state. We strongly urge the
experimental search of the predicted states.
