What are the different types of bonds formed by sulphur with oxygen in thiosulfuric acid?

The molecular structure of thiosulfuric acid ($\text{H}_2\text{S}_2\text{O}_3$) features a central sulfur atom bonded to three oxygen atoms and one terminal sulfur atom. This sulfur-oxygen bonding consists of one $\text{S}=\text{O}$ double bond and two $\text{S}-\text{O}$ single bonds.

$\text{HO}-\text{S}-\text{OH}$ $|$ $\text{S}=$ $\text{O}$

The central sulfur thus forms one double bond and two single bonds with oxygen atoms.