Gwent Police said: “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.”
Reform MS Llyr Powell said there would be a “formal process in which the group decides who is now going to lead it” when asked if Reform’s Welsh deputy Helen Jenner would take charge.
He told the Senedd Sources podcast that a new leader was expected to be chosen by the end of the month.
Asked about Mr Thomas’s mood, he said his former party leader was “panicking” after announcing his resignation at the thought of “this being relived in everyone’s living rooms”.
“We need to all remember there are human beings at the end of this,” he added.
Plaid Cymru Senedd group chair, Marc Jones, said: “Reform UK is descending into chaos.”
He added: “Sarah Cooper-Lesadd’s decision to leave and join Plaid Cymru says it all – Reform is interested in division and headlines, not governing Wales.”
Ken Skates, leader of Welsh Labour, told the Press Association: “This is quite incredible news and many questions will need to be answered.
“Dan Thomas was a personal pick by Nigel Farage and this will surely demonstrate the appalling judgement of the Reform UK leader.”
Mims Davies, the Conservative Shadow Secretary of State for Wales said: “Reform are hitting the news for all the wrong reasons – massive crypto donations, on top of the jailing of Nathan Gill for pro-Russian bribery.
“All this raises serious and deep questions about Reform’s judgement and leadership at every level.”
Welsh Liberal Democrat Leader, Jane Dodds, said: “The wheels are rapidly coming off Reform in Wales and the entire country.”
