Reform said Tuesday that Thomas was not taking part in a parliamentary question session with the first minister of Wales for “personal reasons.”
Gwent Police said in a statement reported by multiple media outlets: “On Sunday 13 September a 45-year-old man, from the Aberbargoed area, was arrested on suspicion of assault and engaging in controlling/coercive behaviour.
“He has been bailed pending further enquiries.”
Thomas was only picked as Reform’s Welsh party leader in February, and became the leader of the opposition in the devolved assembly in May after a strong showing by Farage’s outfit in national elections.